Visiting winger Ivan Cavaleiro’s first-half goal proved the difference in what was a tight and scruffy encounter at the KCOM Stadium.
The Tigers had their moments in the second half but failed to claim a victory which could have taken them above the Cottagers in the Championship table.
Speaking after the game, Pennington said: “It was a frustrating one for all of us. It was a real chance for us to make our mark and push on up into the play-offs against a side that was just above us in the table.
“As you would expect, everyone was disappointed that we failed to take that opportunity.
“There wasn’t too much between the two sides over the 90 minutes and neither side created too many chances. Ultimately, one bit of quality decided the game.
“Fulham slowed the game down well after the goal. They made it hard for us to break them down and we struggled to create any clear-cut chances.
“It was disappointing to lose again at home because we know we need to be strong at the KCOM and make it a real fortress.
“Every side wants to win their home games and we are no different but, in saying that, you have to win away as well. We need to win every game we can to give ourselves the best possible chance of achieving our goals.
“As disappointing as it was on Saturday, we’ll go through the game, see where we can improve and where we can be better. Hopefully, we can bounce back and return to winning ways next weekend.”