 Over the next few years Masiello cemented himself as a starting centre-back for Atalanta under Gian Piero Gasperini, leading them to a historic 3rd place finish in the 2018–19 season, earning them qualification to the 2019–2020 Champions League Group Stage.One of Masiello's most important contributions to the season came on 22 April 2019 against Napoli where he made an incredible goal line clearance in the 50th minute to keep the game at 1–0 for Napoli.Atalanta would go on to win that game 2–1 earning Atalanta three vital points in their push for a top four finish.