Second half goals from Tim Hoogland and Hugo Rodallega won the tie, and gave Symons two consecutive victories following the defeat of Doncaster in the League Cup.
Despite struggling in the first half at St Andrews, the Cottagers looked revitalised in the second period, dominating the game and being rewarded for their confident display with a win that will return more confidence to the West Londoners.
Symons was delighted to see his squad pick up their first three points of the Championship campaign, although he too was disappointed with the first half display, and is looking for more consistency across the full 90 minutes.
Speaking to the official Cottagers website, the Welshman said: “I’m absolutely delighted for the players, for the fans and for the whole Football Club.
“Winning breeds confidence and gives you momentum. That’s what we’ve got now, two wins on the spin, and we need to build on it.
“It’s a start, and that’s all it is. But it’s a great start to have. Belief was the word we spoke about before the game, and at half-time, because I don’t think we really showed the belief in the first half but in the second half we showed it in abundance.”
Belief and character have been traits not seen at Craven Cottage since the arrival of former head coach Felix Magath last season, and Symons was determined to bring passion out of the players for the second half.
"[I told them to] liven up a bit because we didn’t get going at all,” he added.
“Our defending was a little bit loose and our passing was absolutely awful. We were overplaying in the wrong areas and it was a poor first-half performance.
“Birmingham were the better side and they deserved their lead.
“But the players took on board what we told them at half-time, what we asked them to do differently, and they came out and did it fantastically well.
“We got two goals and then we could have got a couple more. Although they were pushing for the equaliser, our goal looked pretty solid, pretty safe and we looked more likely to score the next goal as well.
“In the three games since I’ve taken over, we seem to do either very well first half and drop off in the second half or the other way. If we could actually start playing well for 90 minutes of football, it’d be a doddle this job but unfortunately it’s not quite as simple as that."