Stone were thrown at two actors from a passing car in what is being described as a “homophobic hate crime”.
The “cowardly attack” happened “because we were embracing”, one of the actors said.
A stone struck one of them in the face during “aggressive ignorance from strangers to other strangers”.
It led to the production they were appearing in – Rotterdam at the NST Campus theatre in Southampton – to be cancelled on Saturday.
The actors were “hugely shaken” by what happened, a statement on the production’s Twitter account said.
In a series of tweets, producers said the actors had been “assaulted on their way to work”.
They added: “The assailants verbally abused them and threw stones from their car window, one of which struck an actor in the face.
“They have sustained only minor injuries but are hugely shaken from this cowardly, homophobic hate crime.”
The unnamed actor who spoke out said: “The attack happened because we were embracing. There’s no mistake that this was a homophobic hate crime.
“It was a cowardly attack as it was a moving car. Our community shouldn’t have to tolerate this.
“This is why we have Pride. We should take all steps we can in the education system to help to eradicate this aggressive ignorance from strangers to other strangers.”
It follows a violent attack on a gay couple on a bus in London, during which two women were attacked and punched several times.
Rotterdam is about a gay woman whose girlfriend tells her she has always identified as a man and wants to start living as one.
It is described as a “bittersweet comedy about gender, sexuality and being a long way from home”, and is touring the country after a run in the West End.
After cancelling Saturday’s performances, the theatre said it was “devastated that this kind of behaviour is still so prevalent, a fact which reinforces the importance of this play’s message”.
Anyone with information is being urged to contact the police.