Children's writer and illustrator Anthony Browne, formerly of Hipperholme, opened the historic building, which has undergone a £700,000 refurbishment.
The library at Rydings Park, Halifax Road, has been through an extensive restoration programme and now includes a new layout, refreshment area, lift to the upper floor, and improved toilets and baby-changing areas.
Work began at the start of the year and during that time the library has been based at the former Pennine Housing 2000 offices in Lawson Road, Brighouse.
At the opening, Year 5 and 6 pupils of St Andrew's Junior School, Brighouse, St Chads CE Primary School, Brighouse, and Woodhouse Primary School, Brighouse, took part in a self portrait competition.
The winner of the competition went home with a copy of one Mr Browne's books.
Speaking about the unveiling, Mr Browne, who has written and illustrated 30 titles, said: "It is great to see the gallery and library in one place. Brighouse is lucky to have this wonderful building."
Joining him at the unveiling was Mayor of Calderdale Conrad Winterburn and Deputy Mayor David O'Neill.
During the opening Friends of the Rydings held a special a tree-planting ceremony.