Dekker was born at Gatooma in Mashonaland in what was then Rhodesia in 1969, his family having previously lived in South Africa. He grew up in Bulawayo and was educated at Christian Brothers College where he first played regular cricket. He played for the Zimbabwe under-15 team and for Zimbabwe schools.

After leaving school Dekker played in England for Central Lancashire Cricket League side Crompton Cricket Club in 1988 and 1989 and by 1990 was playing in Zimbabwe for Old Miltonians and Matabeleland before the province was given first-class cricket status. He played for Young Zimbabwe against Pakistan B in a match later given declared first-class and in other matches against other touring teams and "scoring plenty of runs in domestic cricket" as an opening batsman when he was "surprised" to be included for the Zimbabwe national team to play a One Day International (ODI) against New Zealand in October 1992.^[2]

A Test call up followed in December 1993 and Dekker went on to play 14 Test matches and 23 ODIs for Zimbabwe, his final international appearances coming at the end of 1996. He was the first batsman in Zimbabwe's history to carry his bat through a completed Test innings, scoring 68 not out against Pakistan at Rawalpindi in 1993.^[2]

After retirement Dekker coached cricket at Tonbridge School in Kent, England. In 2017 he was appointed as a Community Cricket Officer at Kent County Cricket Club.^[4]