The Men in Black were down 13-12 at the break after Gloucester's Dan Murphy scored the first half's only try and the visitors led 20-15 in the second, before a Richard Wigglesworth try and the boot of Charlie Hodgson saw Sarries home.
The result was the perfect response to a disappointing 12-3 defeat to Worcester last week and McCall praised his players' resilience.
"It was very important today that we got a win and I thought we dealt with some set-backs pretty well - we didn't do that last week," McCall said.
"We responded well to their charge-down try and then we responded from what was from our point of view a soft second try as well.
"I thought we came back very well too, we really upped our intensity and physicality in those periods. The team showed a lot of character today."
A dramatic finale saw Gloucester exert some heavy pressure on the Saracens defence but the hosts held firm and McCall praised young Nick Auterac who came off the bench in the dying minutes.
McCall said: "We took Rhys Gill off with three minutes to go who was scrummaging well and we brought on a 19-year-old in Nick Auterac who hasn't got much premiership experience.
"It probably wasn't the kindest thing I've ever done to Nick but our last scrum was amazing - Nick's a really talented kid who has come through our academy and he's got a big future."