Because of an injury, Thiago could not play his club's first competitive match of the season, in the 2017 DFL-Supercup where Bayern won against Borussia Dortmund 5–4 on penalties on 6 August 2017. On 26 October, he scored an equalizing goal against RB Leipzig to make it 1–1 and later Bayern went on to win the DFB-Pokal second-round match 5–4 on penalties. On 23 November, he was substituted in the 44th minute of the match as he suffered a serious muscle injury in his thigh in Bayern's 2–1 away victory over R.S.C. Anderlecht in the Champions League group stage match and was confirmed by his club manager Jupp Heynckes that he will be out for a long period of time. Thiago was back in the starting lineup and made his first appearance since his injury in November in a 2–1 away victory over VfL Wolfsburg on 17 February 2018. On 4 April, he scored a header which secured Bayern Munich a 2–1 away victory over Sevilla FC in the first leg of their Champions League quarter-final tie. He finished the season with seven goals in 31 appearances.