Born in Crete, Giakoumakis began playing football for Olympiakos Chersonissos and started his professional career after moving to Atsalenios in 2011.
During his last season with the club Petros Giakoumakis scored 19 goals in 25 appearances, however his contribution was not enough for Atsalenios to remain in the Football League 2 and were relegated to the Heraklion FCA championships for the first time in 18 years.
[2] His good performances with Atsalenios did not go unnoticed by a number of Superleague clubs, with Panionios and OFI showing interest in signing the young forward for the summer transfer period of 2014.
[6] He scored a last-minute winner from Clarck N'Sikulu's assist at home to OFI Crete on 24 November.
Each move was either on a free transfer or following loan spells, showcasing his adaptability across Greek and international football markets.