The 24-year-old, who was nominated in February, has gone one better thanks to four goals in five games during March.
All of Eisa's strikes came in the away victories at Swindon Town and Crawley Town, where he also won a penalty.
"It is a great and thoroughly deserved accolade for Mo and rich reward for his excellent form over the last few months," Cheltenham manager Gary Johnson told the EFL website.
"Mo has enjoyed a wonderful first full season in the Football League. He is learning and getting better with every game and hopefully the fact that his ability has been recognised and rewarded in this way will now spur him on to finish the season really strongly."
Eisa added: "I am absolutely delighted to get the award. I was nominated last month too and came close then so it is nice to go one better and be named as the winner. It's been a good March for both me and the team, with some positive results especially on the road.
"It's always great to win any award and I thank my teammates for the part they played in helping me achieve this. Now I just want to use it as a springboard to kick on and perform well until the end of the season."