Police took the would-be bandits into custody after they were apprehended by an off-duty police officer and bystanders.
The armoured car was parked in front of a post office in the centre of Mariehamn when two young masked men drove up on mopeds. One of the men entered the vehicle and people nearby reported hearing gunshots.
After the shots, the robber jumped back on his moped and attempted to escape along a pedestrian walkway. An off-duty policeman managed to block the robbers' getaway by throwing an outdoor advertising sign in front of them.
The vehicle was carrying the day's takings from the Ålandstravet horse racetrack along with other valuables.
Several shots were fired during the incident, but police have declined to confirm how many. One bystander, a Swedish man, and one of the vehicle guards sustained minor gunshot injuries. The guard was treated in hospital after being grazed by several bullets.
On Monday afternoon police said the two men detained since Sunday, aged 20 and 27, are well known to police in Sweden.
The Åland Islands are a semi-autonomous Swedish-speaking region of south-west Finland.