Amazon’s bid to be a Prime mover during TV’s annual Upfront Week is causing it to crash into long-held industry protocols.

The streaming and e-commerce giant plans to shift its upfront presentation to the Monday evening of the week of May presentations that top media companies hold annually for Madison Avenue. In doing so, Amazon will likely force some advertisers to abandon other events that have long been held in that slot. Fox Corp. traditionally holds an upfront presentation late Monday afternoon, while NBCUniversal’s Spanish-language Telemundo network has for the past several years held a Monday-night event and concert for advertisers.

Rivals believe Amazon’s maneuver will make Mondays more manic. What’s more, the new event is likely get in the way of not only their scheduled presentations, but ancillary meetings that have already been set between advertisers and the networks’ sales executives.

“The Upfronts are...