Akinde will vie with Charlie MacDonald, Ben Strevens and Carl Cort for a place up front at Griffin Park.
Scott said: "We've been looking at John for a long time, but he was involved with the first team at Bristol City.
"We've persevered with it and fortunately Gary Johnson has let him come to us. He's a big, strong lad who has done well before, and hopefully he'll fit into our side perfectly.
"John's a little bit different to Strevs and Cort. He's quick and powerful and has a little bit of an extra dimension that we haven't got."