Does battle cry trigger for each attacking creature with battle cry separately?

Battle cry is a triggered ability that triggers whenever the creature with it attacks. Each creature with battle cry generates its own separate trigger when it attacks (CR 702.91a). These triggers are independent of one another and each resolves separately on the stack.

When each battle cry trigger resolves, it gives all other attacking creatures +1/+0 until end of turn (CR 702.91b). Because the triggers stack and resolve individually, having multiple creatures with battle cry creates a multiplying effect across your attacking team.

For example, if you attack with two creatures that both have battle cry — say two copies of Hero of Bladehold tokens or similar — each one's trigger fires. When both triggers resolve, every other attacker gets +1/+0 from the first trigger and another +1/+0 from the second trigger, for a total bonus of +2/+0. The creatures with battle cry do not boost each other from the same trigger, but each does receive the boost from the other's trigger.

So with three attackers all having battle cry, each attacker receives +2/+0 (one boost from each of the other two battle cry triggers), demonstrating how powerful multiple battle cry creatures can be in a single attack.