The impressive Lucy Staniforth was on target from 12 yards with 14 minutes left as fine margins proved pivotal at The Hetton Centre.
In a tight opening period, Sunderland’s Staniforth looked the most likely to break the deadlock but a low stop from Caitlin Leach denied the midfielder in the 27th minute before she sent a rasping 25-yard free-kick against the bar three minutes before half-time.
The game sparked into life seconds after the interval, with Abbey Joice forcing a fine fingertip save from Leach with a 20-yard rocket destined for the top corner.
Seemingly, long-range strikes were the order of the day as Jodie Brett responded with her own from the edge of the box in the 54th minute, but it was pushed clear smartly by Anke Preuss as Bristol rallied.
The game was opening up by this point and 11 minutes later, the visitors could have led when Claire Emslie slotted wide after Preuss had saved.
But it would be the hosts who would make the crucial breakthrough, Staniforth netting from the spot after Joice tempted Hayley Ladd into a challenge in the box.
Claire Emslie, Bristol City forward, added:
“We are disappointed to lose the game from a penalty. We did create chances but we need to be more clinical.
“We definitely put in a better performance which we can look to build on in the next few games. “Sunderland are a really good team, the difference is we are a young team. We are still learning and getting used to this level but I think there wasn’t a lot in it.
“We did well to keep it at 0-0 and possibly could have gone ahead. For us it is a learning experience.
“The biggest thing is to be clinical in front of goal. We are not going to get as many chances as we did last year so when we do get that chance we need to put it in the back of the net.”
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