After Katarina Barley's appointment as Federal Minister of Family Affairs, Senior Citizens, Women and Youth, he briefly returned to the office from 2 June to 8 December 2017.

Between 2009 and 2017, Heil served as deputy chairman of the SPD's parliamentary group, under the leadership of successive chairmen Frank-Walter Steinmeier (2009–2013) and Thomas Oppermann (2013–2017), the first four years in the opposition and the other four as a government party.

[4] In the negotiations to form a second grand coalition under Chancellor Angela Merkel and return to the government following the 2013 federal elections, Heil led the SPD delegation in the working group on economic affairs; his co-chair from the CDU/CSU was Ilse Aigner.

[6] In the negotiations to form the third grand coalition under Merkel, he led the working group on education policy, alongside Annegret Kramp-Karrenbauer, Stefan Müller and Manuela Schwesig.

[7] Since becoming Minister of Labour and Social Affairs when the SPD joined the fourth Merkel cabinet in a grand coalition following the 2017 German federal election, Heil has overseen a number of legal measures to strengthen workers' rights, including a law forcing logistics and eCommerce companies to ensure that their subcontractors pay proper social security contributions for their drivers,[8] and the introduction of a higher basic pension for low-income workers.

[10] At a SPD national convention in 2019, Heil was elected as one of the five deputies of the party's co-chairs Saskia Esken and Norbert Walter-Borjans, alongside Klara Geywitz, Kevin Kühnert, Serpil Midyatli and Anke Rehlinger.

[14][15] He also led efforts to fast-track work permits and visas for several thousand foreign airport workers, mainly from Turkey, to help to ease staffing shortages in the tourism sector after a series of COVID-19 lockdowns.

[16] In October 2023, Heil participated in the first joint cabinet retreat of the German and French governments in Hamburg, chaired by Scholz and President Emmanuel Macron.