Tendai Biti, secretary general of the rival Movement for Democratic Change, said the outbursts during the televised speech, which included singing and chanting, were meant to send a message to Mugabe and his ruling ZANU-PF party.
"We attended to protect the fundamental (integrity) of our parliament, and to show that we now control the parliament," Biti told CNN.
The MDC had objected to the convening of parliament at a time when Mugabe and opposition leaders were negotiating a power-sharing agreement.
Tuesday marked the first time an opposition leader had been speaker of the African nation's parliament. Lovemore Moyo, the MDC's national chairman, was elected to the post Monday on a 110-98 vote over a candidate from an MDC faction who had the support of ZANU-PF.