Daniel Altmaier defeated Hamad Medjedovic 7–5, 6–7, 7–6, 6–7, 6–4 in the first round of the US Open on hard court on 26 August 2025, claiming a significant upset over the pre-match favourite. Medjedovic entered as the odds-on favourite at 1.34 to Altmaier's 3.53, but the German outlasted his opponent through a gruelling five-set encounter that saw both players trade tight tiebreaks. The match featured four sets that went to either tiebreak or close scorelines, demonstrating the competitive nature of the contest. Altmaier's ability to recover from losing the second and fourth sets proved decisive in the fifth, where he broke through to secure the victory. The result represents a valuable win for Altmaier against a seeded opponent in the opening round.