Toomaga-Allen re-established his place as a regular starter for the Hurricanes in 2017, starting against the British & Irish Lions on 27 June in a 31–31 draw.
Toomaga-Allen also started in the knockout rounds of Super Rugby that year, but the Hurricanes lost the semi-final to the Lions in Johannesburg 44–29.
After season-ending injuries to Joe Moody and Owen Franks, Toomaga-Allen was re-called to the All Blacks for the 2017 Rugby Championship but did not make an appearance for New Zealand that year until the 2017 end-of-year tour where he came off the bench against the 31–22 win against the Barbarians, replacing Ofa Tu'ungafasi with 13 minutes left.
Toomaga-Allen missed the first few rounds of the 2018 Super Rugby season due to injury but returned off the bench on 24 March 2018, during a 29–12 victory over the Highlanders.
After a good Super Rugby season, Toomaga-Allen was retained by the All Blacks for their 2018 Steinlager series against France, but he did not play in any of the three tests.
Toomaga-Allen was not initially selected for the 2018 Rugby Championship, with newcomers Karl Tu'inukuafe and Tim Perry the preferred option for the All Blacks selectors.
Toomaga-Allen moved to England to join top English Premiership side Wasps on an undisclosed-length deal from the 2019–20 season.