The Brazil forward, who was this week subjected to more racist abuse from rival fans, leading to his club filing a complaint with the Spanish legal authorities, fired Real in front after just four minutes.
Although Osasuna hit back through Ante Budimir, a well-taken goal from Real captain Dani Carvajal had the hosts ahead at the break.
Brahim Diaz scored a third on the break just after the hour mark before Vinicius slotted in his second of the afternoon and Iker Munoz struck a late consolation for the visitors.
Advertisement
Carlo Ancelotti’s side, who were missing England midfielder Jude Bellingham through suspension, made a bright start.
Vinicius gave them an early lead when he took the ball off Osasuna defender Alejandro Catena and ran through to beat the goalkeeper in the fourth minute.
The Brazilian then saw another chance saved after he tried to round keeper Sergio Herrera and Osasuna hit back when Budimir scored from a corner.
Los Blancos, though, regained the lead in the 17th minute when Carvajal latched on to a chipped pass from Federico Valverde to hook the ball in with the outside of his boot.
Advertisement
Following such a frantic start there was a brief lull before Osasuna forward Jose Arnaiz fired another chance over and then Vinicius saw his effort fly just wide before Antonio Rudiger’s header was blocked.
As half-time approached Arnaiz’s curling shot from outside the box was saved by Real keeper Andriy Lunin at full stretch.
Vinicius needlessly picked up a yellow card for dissent when laughing at a decision from referee Martinez Munuera before the break, meaning he will be banned for the LaLiga game against Athletic Bilbao after the international break.
Real, who will face Manchester City in the Champions League quarter-finals, further extended their lead on the hour mark when Diaz raced on to a long kick up field from Lunin, which had been flicked on by Valverde.
Vinicius got his second goal soon after as Valverde turned provider again.
He chested the ball into the path of the Brazilian, who ran into the left side of box and slotted a low shot into far corner for a sixth goal in his past four appearances.
Rodrygo saw his late effort saved before Lucas Vazquez had a goal ruled out for offside.
In stoppage time, Munoz pulled another goal back for Osasuna and 19-year-old Turkish midfielder Arda Guler almost added a fifth for Real when his long-range chip from just past the halfway line dropped on to the crossbar.
