Grammar › N1 · 14 Set expressions and idioms
〜がてら: while; on the occasion of
N1 · 14 Set expressions and idioms
Says you do another thing on the occasion of doing the main one.
Noun or verb stem + がてら + movement verb: 散歩がてら, 買い物がてら. Casual to neutral. The second action is the main one. Compare 〜かたがた (formal), 〜ついでに (by the way).
Examples
散歩がてら、パンを買いに行った。
I went to buy bread while out for a walk.
通勤がてら、郵便局に寄ってきた。
I stopped at the post office on my way to work.