Laurie Evans scored a record-breaking 118 as Surrey beat Glamorgan by 65 runs at Sophia Gardens.
After choosing to bat first, Surrey posted the highest-ever score at the Cardiff ground of 236/2, with Evans making the highest-ever individual T20 score against the Welsh county.
Sam Northeast made 76 in the run chase but Glamorgan fell far short of the victory target, in a night-to-forget for the home side.
"Surrey played very well tonight," said Northeast.
"Laurie Evans and Will Jacks started brilliantly with the bat and then Sam Curran came in and played a great knock as well and 230 was just a bit too much tonight. If it was somewhere near 200 to chase then it might have been a different run chase but 230 was too many.
"They bowled pretty well at stages there as well and it was a tough night."