diff --git a/Koha/REST/V1/Libraries.pm b/Koha/REST/V1/Libraries.pm
index 544164f602..2975bc9a89 100644
--- a/Koha/REST/V1/Libraries.pm
+++ b/Koha/REST/V1/Libraries.pm
@@ -18,7 +18,10 @@ package Koha::REST::V1::Libraries;
 use Modern::Perl;
 
 use Mojo::Base 'Mojolicious::Controller';
+use C4::Context;
 use Koha::Libraries;
+use Koha::Calendar;
+use Koha::DateUtils qw( dt_from_string );
 
 use Scalar::Util qw( blessed );
 
@@ -209,4 +212,54 @@ sub list_cash_registers {
     };
 }
 
+=head3 list_holidays
+
+Controller function that returns closed days for a library within a date range.
+Used by booking calendar to disable selection of closed days.
+
+=cut
+
+sub list_holidays {
+    my $c = shift->openapi->valid_input or return;
+
+    my $library_id = $c->param('library_id');
+    my $from       = $c->param('from');
+    my $to         = $c->param('to');
+
+    my $library = Koha::Libraries->find($library_id);
+
+    return $c->render_resource_not_found("Library")
+        unless $library;
+
+    return try {
+        my $from_dt = $from ? dt_from_string( $from, 'iso' ) : dt_from_string();
+        my $to_dt   = $to   ? dt_from_string( $to,   'iso' ) : $from_dt->clone->add( months => 3 );
+
+        if ( $to_dt->compare($from_dt) < 0 ) {
+            return $c->render(
+                status  => 400,
+                openapi => { error => "'to' date must be after 'from' date" }
+            );
+        }
+
+        my $calendar = Koha::Calendar->new( branchcode => $library_id );
+        my @holidays;
+
+        my $current = $from_dt->clone;
+        while ( $current <= $to_dt ) {
+            if ( $calendar->is_holiday($current) ) {
+                push @holidays, $current->ymd;
+            }
+            $current->add( days => 1 );
+        }
+
+        return $c->render(
+            status  => 200,
+            openapi => \@holidays
+        );
+    } catch {
+        $c->unhandled_exception($_);
+    };
+}
+
 1;
diff --git a/api/v1/swagger/paths/libraries.yaml b/api/v1/swagger/paths/libraries.yaml
index 1f06fd4cea..6c3e1fbb2a 100644
--- a/api/v1/swagger/paths/libraries.yaml
+++ b/api/v1/swagger/paths/libraries.yaml
@@ -425,6 +425,62 @@
     x-koha-authorization:
       permissions:
         catalogue: 1
+"/libraries/{library_id}/holidays":
+  get:
+    x-mojo-to: Libraries#list_holidays
+    operationId: listLibraryHolidays
+    tags:
+      - libraries
+    summary: List holidays for a library
+    description: |
+      Returns a list of closed days (holidays) for a library within a date range.
+      Used by booking calendar to disable selection of closed days.
+    parameters:
+      - $ref: "../swagger.yaml#/parameters/library_id_pp"
+      - name: from
+        in: query
+        description: Start date for the range (ISO 8601 format, e.g., 2024-01-01). Defaults to today.
+        required: false
+        type: string
+        format: date
+      - name: to
+        in: query
+        description: End date for the range (ISO 8601 format, e.g., 2024-03-31). Defaults to 3 months from 'from'.
+        required: false
+        type: string
+        format: date
+    produces:
+      - application/json
+    responses:
+      "200":
+        description: A list of holiday dates in YYYY-MM-DD format
+        schema:
+          type: array
+          items:
+            type: string
+            format: date
+      "400":
+        description: Bad request
+        schema:
+          $ref: "../swagger.yaml#/definitions/error"
+      "404":
+        description: Library not found
+        schema:
+          $ref: "../swagger.yaml#/definitions/error"
+      "500":
+        description: |
+          Internal server error. Possible `error_code` attribute values:
+
+          * `internal_server_error`
+        schema:
+          $ref: "../swagger.yaml#/definitions/error"
+      "503":
+        description: Under maintenance
+        schema:
+          $ref: "../swagger.yaml#/definitions/error"
+    x-koha-authorization:
+      permissions:
+        catalogue: "1"
 /public/libraries:
   get:
     x-mojo-to: Libraries#list
diff --git a/api/v1/swagger/swagger.yaml b/api/v1/swagger/swagger.yaml
index d8f3b4ccaa..01ea17d163 100644
--- a/api/v1/swagger/swagger.yaml
+++ b/api/v1/swagger/swagger.yaml
@@ -499,6 +499,8 @@ paths:
     $ref: "./paths/libraries.yaml#/~1libraries~1{library_id}~1cash_registers"
   "/libraries/{library_id}/desks":
     $ref: "./paths/libraries.yaml#/~1libraries~1{library_id}~1desks"
+  "/libraries/{library_id}/holidays":
+    $ref: "./paths/libraries.yaml#/~1libraries~1{library_id}~1holidays"
   "/oauth/login/{provider_code}/{interface}":
     $ref: ./paths/oauth.yaml#/~1oauth~1login~1{provider_code}~1{interface}
   /oauth/token:
diff --git a/t/db_dependent/api/v1/libraries.t b/t/db_dependent/api/v1/libraries.t
index e775a79917..35db436b26 100755
--- a/t/db_dependent/api/v1/libraries.t
+++ b/t/db_dependent/api/v1/libraries.t
@@ -18,7 +18,7 @@
 use Modern::Perl;
 
 use Test::NoWarnings;
-use Test::More tests => 8;
+use Test::More tests => 9;
 use Test::Mojo;
 use Test::Warn;
 
@@ -27,6 +27,7 @@ use t::lib::Mocks;
 
 use List::Util qw(min);
 
+use Koha::Caches;
 use Koha::Libraries;
 use Koha::Database;
 
@@ -438,3 +439,100 @@ subtest 'list_cash_registers() tests' => sub {
 
     $schema->storage->txn_rollback;
 };
+
+subtest 'list_holidays() tests' => sub {
+
+    plan tests => 16;
+
+    $schema->storage->txn_begin;
+
+    my $library = $builder->build_object( { class => 'Koha::Libraries' } );
+    my $patron  = $builder->build_object(
+        {
+            class => 'Koha::Patrons',
+            value => { flags => 4 }
+        }
+    );
+    my $password = 'thePassword123';
+    $patron->set_password( { password => $password, skip_validation => 1 } );
+    my $userid = $patron->userid;
+
+    my $branchcode = $library->branchcode;
+    my $cache      = Koha::Caches->get_instance();
+
+    # Clear existing holidays for this branch
+    $schema->resultset('SpecialHoliday')->search( { branchcode => $branchcode } )->delete;
+    $schema->resultset('RepeatableHoliday')->search( { branchcode => $branchcode } )->delete;
+    $cache->clear_from_cache( $branchcode . '_holidays' );
+
+    # Add a specific holiday
+    $builder->build(
+        {
+            source => 'SpecialHoliday',
+            value  => {
+                branchcode  => $branchcode,
+                day         => 15,
+                month       => 6,
+                year        => 2026,
+                title       => 'Test holiday',
+                description => '',
+                isexception => 0,
+            },
+        }
+    );
+
+    # Add a second holiday
+    $builder->build(
+        {
+            source => 'SpecialHoliday',
+            value  => {
+                branchcode  => $branchcode,
+                day         => 20,
+                month       => 6,
+                year        => 2026,
+                title       => 'Another holiday',
+                description => '',
+                isexception => 0,
+            },
+        }
+    );
+    $cache->clear_from_cache( $branchcode . '_holidays' );
+
+    # Returns holidays within range
+    $t->get_ok("//$userid:$password@/api/v1/libraries/$branchcode/holidays?from=2026-06-01&to=2026-06-30")
+        ->status_is(200);
+
+    my $holidays = $t->tx->res->json;
+    ok( ( grep { $_ eq '2026-06-15' } @$holidays ), 'First holiday found in response' );
+    ok( ( grep { $_ eq '2026-06-20' } @$holidays ), 'Second holiday found in response' );
+
+    # Returns empty list when no holidays in range
+    $t->get_ok("//$userid:$password@/api/v1/libraries/$branchcode/holidays?from=2026-07-01&to=2026-07-05")
+        ->status_is(200);
+
+    my $no_holidays = $t->tx->res->json;
+    my @filtered    = grep { $_ eq '2026-06-15' || $_ eq '2026-06-20' } @$no_holidays;
+    is( scalar @filtered, 0, 'No test holidays outside their range' );
+
+    # 400 when to < from
+    $t->get_ok("//$userid:$password@/api/v1/libraries/$branchcode/holidays?from=2026-06-30&to=2026-06-01")
+        ->status_is(400)
+        ->json_is( '/error' => "'to' date must be after 'from' date" );
+
+    # 404 for non-existent library
+    my $non_existent_code = $library->branchcode;
+    $library->delete;
+    $cache->clear_from_cache( $non_existent_code . '_holidays' );
+
+    $t->get_ok("//$userid:$password@/api/v1/libraries/$non_existent_code/holidays?from=2026-06-01&to=2026-06-30")
+        ->status_is(404)
+        ->json_is( '/error' => 'Library not found' );
+
+    # Defaults work (no from/to params)
+    my $library2 = $builder->build_object( { class => 'Koha::Libraries' } );
+    $t->get_ok( "//$userid:$password@/api/v1/libraries/" . $library2->branchcode . "/holidays" )
+        ->status_is(200)
+        ->json_is( '' => [], 'Empty holidays for fresh library with defaults' );
+
+    $schema->storage->txn_rollback;
+};