Joe Mills and Karen Hazzard were the only singles winners from the county at the Sussex Open Championships at West Worthing.
The prestigious event had six junior age group categories and attracted entries from all over the South.
Joe beat favourite Nick Greenaway (Hove) 7-6 6-1 in the ten-and-under final.
He said: "It is the best win I've had. Nick got a bit angry after losing the first set on a tie-break. That helped me.
"It is the first time I've played with umpires and it was a bit frustrating. I was doing aces and getting foot-faulted."
Joe is in great form. The ten-year-old, from Hove, said: "When I beat Nick it was my 19th win in a row.
"I've won 44 games at LTA Ratings events in six months. I think I've done quite well. I have lost, but I don't keep a record of those!"
He wants more success in the Sussex Closed Championships at Southdown, Lewes, next week.
Joe said: "I haven't played at the Closed before but I think I will be among three players who are favourites to win it. Winning the Open has given me a lot of confidence.
"I will get another chance to play my matches with an umpire if I get beyond the group stage."
He is coached by Martin Reeves at Pavilion and Avenue. His mother, Julia, plays for Preston Park and he will be joined at the Closed by brother Sam, 13.
Joe said: "Hopefully we will do well. I've played for three years and am quite serious about my tennis.
Sussex's only success in the girls' singles came at 18 and unders when Karen Hazzard (Crawley) beat Nicola Gerrett (Crowborough) 6-3 6-3 in the final.
Miles Bugby, from Storrington and a West Worthing member, was beaten 1-6 6-4 6-2 by Nimrod Perel (Middlesex) at 18-and-under.
Ben Reeves, nephew to Martin, lost 6-1 6-2 to Tom Beach (Dorset) in the 16-and-under final and James Iswariah (Uckfield) lost 6-2 7-5 to Tim Dean (Berkshire) at 14-and-under.
Felix Gregory (Battle) was beaten 6-1 6-1 by Craig Veal (Hampshire) at 12-and-under.
Alice Barnes, the Cambridgeshire player coached by Lewes' Nigel Sears at Falmer, won two titles.
She took the 21-and-under crown with victory against Gail Atherton (Lancashire) 6-1 6-2 and defeated Sussex captain Julie Hanger (Horsham) 6-3 6-1 in the ladies' senior event.
In the doubles, Iwariah and Peter Manthorpe (Brighton) were beaten 6-4 6-3 by Hampshire pair William Allen and Alistair Byron at 13-and-under.
The referee was Andy Fyfe,who manages Goran Ivanisevic, the 2001 Wimbledon champion, and Marat Safin, the United States Open title-holder on behalf of Ion Tiriac when they are in England.
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