Holloway had to wait until Marc Bircham's strike in the 84th minute to be sure of the three points his promotion-chasers needed. And he had praise for Town's showing at Loftus Road that held his team for so long.
He said: "I was pleased with they way my boys stuck at it because we didn't realise how deep Grimsby's back line was going to be.
"We had to adjust our game plan a little but it paid off in the end, though they were hard to wear down.
"There wasn't a great deal to trouble us at the back but maybe Grimsby surprised us a little bit - they had a decent spirit and got stuck in.
"We shouldn't have been surprised, though, because they are fighting for their lives and this was a massive game for them."
Despite Town's hard work, they were undone at the back end of both halves by a strike force led superbly by Paul Furlong.
And Holloway was full of praise for the former Chelsea front man.
"Paul did really well today for us but then that's what you expect from him," Holloway added.
"He's big and strong and I would hate to play against him.
"He is the sort of player you need because he is so committed and will throw everything into every challenge.
He deserved his two goals today."