Synonyms for immediately

at once, without delay, instantly, directly, right away, instanter, at the first opportunity, forthwith, straightaway, in a trice, in that instant, at short notice, now, this instant, speedily, quickly, promptly, on the spot, on the dot, rapidly, summarily, instantaneously, unhesitatingly, shortly, tout de suite (French), before you could say Jack Robinson*, on the double*, now or never*, in a jiffy*, straight off*, right off the bat*, pronto*, PDQ*; see also quickly 1, 2.

Antonyms in the future, later*, in a while.