It has welcomed more than 3.5 million visitors since opening in February 2000.
To mark the occasion, the gallery will bring together works of contemporary art collected over the last 20 years, from artists who have featured in the exhibitions and studio programmes.
'It has become a landmark and a meeting place': Walsall's New Art Gallery gears up for 20th anniversary
20:20 - Twenty Years of Collecting Contemporary Art will reflect overlapping themes such as the changing urban landscape, the Black Country, the impact of globalisation and people and places, and will feature work from a selection of international artists as well as those closer to home.
20:20 also includes a range of works by artists who have engaged with the culture and landscape of the Black Country including Rita Donagh, Laura Oldfield Ford, Martin Parr and Mark Power.
The exhibition will acknowledge significant gifts and schemes such as the Contemporary Art Society’s Special Collection Scheme and Art Fund International as well as the Clive Beardsmore Gift, a collection of 200 modern and contemporary works generously donated to the Gallery in 2014.
In an exhibition in the ground floor Community Gallery will be a selection of works by director Stephen Snoddy, representing each individual year of the Gallery’s 20 year history. 20 for 2020 will include works by Gavin Turk, Christopher Le Brun, Soheila Sokhanvari and Jane and Louise Wilson.
The Garman Ryan Collection will be displayed almost in its entirety, complemented by a series of works focusing on the women behind the Collection, Kathleen Garman (widow of Sir Jacob Epstein) and Sally Ryan, created during a residency at the Gallery in 2014 by Birmingham artist Sarah Taylor Silverwood.
Stephen Snoddy, director of The New Art Gallery Walsall, said: “For our 20th birthday celebrations, we are bringing together works of contemporary art from our collections that mark significant moments in our history.
"Our beautiful building will be bursting with a wide range of art works by local, regional, national and international artists. We are immensely proud of our strong track record in supporting artists and exploring fresh and creative ways of connecting artists with audiences.
"We firmly believe that art has the power to inspire, to challenge and to bring people together and hope to continue to advocate the importance of the visual arts for many years to come.”
A preview event open to all will be held on February 20 featuring eminent speakers and a DJ set by Bob and Roberta Smith.
This will be followed on February 22 with Arty Party for all the family featuring music, free workshops, games and birthday cake.