Frank attended St. Columba's School in Ponsonby. Following school he began playing for the
Ponsonby player in the
Auckland Rugby League competition, Delgrosso was first selected for the
New Zealand side in 1921. He made his Test debut against
Great Britain in 1924 and went on to play in nine Test matches. This included captaining New Zealand in the second and third Test matches in 1924. He also played for the Auckland Provincial team in 1924 and scored a try in a 13–28 loss. At the end of 1930 Delgrosso was sensationally suspended for three seasons by the
Auckland Rugby League, which would have effectively ended his career. Delgrosso was accused off failing to get one of his sent off teammates to leave the field, throwing mud at the referee and using foul language. At a management committee meeting in March, 1930 they decided to remit the remainder of his suspension after he apologised for his actions.{{cite news ==Coaching, administrative and refereeing career==