However, they came a lot closer minutes later when Craig Conway got the ball on the left and beat two defenders before cutting back on his right and shooting at goal but his shot was well saved by Jack Butland, who tipped the ball onto the bar.
Despite being on the back foot for most of the half, Barnsley took the lead in the 35th minute when Paddy McCourt played a one-two with Marcus Tudgay inside the area and fired a low shot past Tomas Kuszczak.
After the break, the visitors doubled their lead when Jacob Mellis fired home from close range after he and Tudgay were involved in a good move down the right, which saw the latter slide a pinpoint pass to the midfielder at the near post.
Brighton got themselves back into the game from a corner after Butland had done well to turn an effort from Will Buckley past the post, but he couldn't keep Matthew Upson's headed effort out as the defender powered the ball into the top corner.
The home side made a late surge to find an equaliser and Bruno lifted a ball over the top of the Barnsley defence and Buckley raced onto it and was through on goal but his shot was well saved by Butland, who spread himself big to make the block.