She was a two-time winner of the Dutch Women's Chess Championship (1971, 1972).

From mid-1960s to mid-1970s, Hendrika Timmer was one of the leading Dutch women's chess players.

She twice in a row won Dutch Women's Chess Championships (1971, 1972).

Timmer played for Netherlands in the Women's Chess Olympiads:[2] Timmer grew up in Ermelo and permanently returned to her home town when her parents were aging.

On 7 February 1994, Timmer suffered a heart attack during a chess match in Apeldoorn.