[3][4] He failed to make an appearance outside the Leinster Championship but won a medal as a squad member of the 2016 All-Ireland Champions Dublin.
[6] In July 2017, he won his second Leinster senior football championship with Dublin what proved to be his most prolific game from a scoring point of view.
He scored a total of 0–12 points against Kildare at Croke Park and helped guide Dublin to their seventh consecutive Leinster Championship title.
[1] O'Callaghan won the All-Ireland Under 21 Football Championship with Dublin in 2017, scoring a total of 1–3 against Galway at O'Connor Park.
[1] In the 11th minute of a game against Roscommon, O'Callaghan collected a pass by Brian Fenton from above his head past the "D" and fell onto his twisted right leg.
[1] O'Callaghan rose from the awkward fall without effort, immediately hopped the ball and sent it over the bar for a point.
[1] In the All-Ireland semi-final, he scored two goals past Lee Keegan and took a fierce hit from Mayo goalkeeper Rob Hennelly but was unaffected.