A 72nd-minute penalty from Leigh Griffiths marked a win for Hibs, and following Monday's defeat to St Johnstone, Fenlon was delighted with the change of attitude from his players.
Speaking after the St Mirren Park win - their third in 12 games - Fenlon said: "It's good to be back winning. That's the important thing. Now we've got to make sure we kick on from today.
"If you look at the two performances, we knew on Monday night that the St Johnstone game wasn't us, we were poor. We spoke about it during the week and what we worked on has paid off. I'm delighted with the lads.
"It's a massive three points for us with the league being so tight and that's what makes Monday so disappointing. If you can win your home games then come on the road and pick up something, it can make a massive difference to the table.
"We were a lot better today. Our shape was excellent from start to finish, I thought we passed the ball really well, particularly in the first half, and when we lost the ball we got a lot of numbers back and made it difficult for St Mirren to break us down.
"I don't think they created loads of chances. We had worked on that all week to make sure we stopped that supply into the strikers and Paul McGowan."