The on-loan Fleetwood Town striker picked up the accolade after a string of impressive performances for the Ton.
"I'm delighted. To be picked ahead of Hibs or Rangers players who have played so well is a big thing," he said.
The 21-year old has been used in a more advanced midfield role this season to accommodate team-mate Denny Johnstone up front for the Greenock club.
McManus is in his second loan spell at Cappielow. Following last season's League One success, he admits things are a lot more difficult at Championship level.
"I've only been back here since January but I'm enjoying every minute," he continued.
"We've been getting good results and teams like Rangers and Hibs haven't found it easy against us.
"There are better players in this league, better teams.
"I've played more of an attacking midfield role this season and I've tried to fill in for the team more so the gaffer's happy with me.
"I've still got a few goals and a few assists so I'm happy all round. I hope now to just keep it up."
Last month McManus scored once against Alloa in a 2-2 draw and a brace in a 3-2 defeat by Raith Rovers, both matches away from home.
Morton's Declan McManus has won the Ladbrokes Championship player of the month award for February.