The signing with Minsk city chief executive Andrey Shorets took place as part of a three-day working visit with Ušakovs - sporting his trademark powder blue suit - accompanied by various local government and business figures in a bid to bring the two capitals closer.
The deal covers the period 2015-17 and is aimed at promoting tourism, sharing experiences of local government and greasing the wheels of business.
The trip also coincides with the "Leisure 2015" tourism exhibition at which Ušakovs pointed out that tourist numbers from Belarus to Latvia are rising rapidly even while the numbers from Russia are falling.
The first Riga and Minsk co-operation agreement was signed in 1999.
The sometimes frosty relations between the authoritarian regime of Belarus' Aleksandr Lukashenka have improved since the Russian invasion of Ukraine, with the eccentric and temperamental Lukashenka even cast in the unlikely role of peacemaker acting as an intermediary in peace negotiations despite the fact that EU sanctions against members of his anti-democratic regime remain in place.
Much attention will focus on whether Lukashenka is invited to May's Riga Summit, which is due to discuss the shape of future Belarusian relations with the European Union.
Even more attention will focus on whether he accepts any such invitation.
