The boys' 100 metre breaststroke event at the 2018 Summer Youth Olympics took place on 7 and 8 October at the Natatorium in Buenos Aires, Argentina.

[1] The heats were started on 7 October at 11:00.

[2] The semifinals were started on 7 October at 18:38.

[3] The final was held on 8 October at 19:02.

[4]