The Glovers boss is casting his eye over the 22-year-old forward, who he worked with at Peterborough.
Appiah, who joined the Eagles after scoring 35 goals in 33 games for Margate, has made one start for the Championship club this season as well as seven appearances off the bench.
"We have got Kwesi Appiah with us from Crystal Palace at the moment, training with us," Johnson told This is Somerset.
"He has got that raw pace, he has got that good touch and I do know him so I know what he will bring personality-wise to the squad.
"He has had a couple of games for Palace and he came off the bench against Stoke City in the FA Cup recently."
Yeovil will hope to play their first match for 17 days on Tuesday night when MK Dons visit Huish Park.