The traffic surpassed the BBC’s previous record of 315 million requests, set in January this year, and was helped by surging mobile traffic.
The BBC said that mobiles and tablets accounted for 115 million TV programme requests in the month – almost half of the total 248 million TV show views on the service.
For the first time, TV requests from tablets and PCs were also on a par. Each accounted for 29%, while TV views from mobile devices stood at 18%, from games consoles 5% and from TV platform operators 16%.
Among the most popular shows during March were episodes of auto show Top Gear, singing competition The Voice UK, and comedy series Outnumbered.
The BBC said that, consistent with previous months, the profile of BBC iPlayer users has “evened out over time in terms of male/female ratio, but remains strongly under-55 in terms of age.”
The iPlayer is used for TV at roughly the same time of day as linear TV viewing, although there is proportionally more daytime and late-peak use, the corporation added.