日本語道場 — Nihongo Dojo

～がてら

~gatera

while, on the occasion of

When to use it

Use ～がてら in written or formal speech to say that, in the course of doing A, you also accomplish B — the two actions occupy the same occasion. It is more literary and more restricted than ～ついでに, appearing mostly with movement or social-occasion nouns (挨拶・散歩・出張・見学・行き・帰り). In business writing it softens a secondary request or report by framing it as incidental to an already-planned action.

Formation

Verbs: ます-stem + がてら —「行きがてら」「帰りがてら」「申し上げがてら」. Only volitional, durative-action verbs work.
Nouns: action/verbal noun (する-noun) + がてら —「挨拶がてら」「出張がてら」「視察がてら」. No の or を intervenes.
i-adjectives / na-adjectives: not used.
Plain (non-action) nouns: not used — ✗「本がてら」.
Fairly lexicalized: a handful of set collocations covers nearly all real usage. The clause after がてら names the incidental purpose, and the sentence normally ends in a volitional, request, or past-report form.

Examples

While paying my respects, I'll also hand over the new product materials.
On the occasion of the business trip, I plan to drop by the Osaka branch as well.
While touring the plant, I'd also like to identify issues on the floor.
In thanking you, I would also like to report on our progress.
On my way back, I left the documents at their reception desk.