Antonio has put pen to paper on a new deal at West Ham which will see him remain at the London club until 2020, as announced on their official website on Monday.
Former West Ham striker Harewood has stated on Twitter that the winger deserves the new contract.
Antonio joined West Ham from Championship outfit Nottingham Forest in the summer of 2015.
The 26-year-old winger took some time to adapt to the Premier League, but he ended the 2015-16 campaign strongly.
The former Sheffield Wednesday man scored eight goals and created 24 chances in 26 Premier League matches for the Hammers last season.
Antonio had a pass accuracy of 70% and a shot accuracy of 47%, and won 39 headers, 47 dribbles and 26 tackles.
West Ham have already started pre-season training, as they prepare for the upcoming 2016-17 campaign.
Slaven Bilic’s side will be aiming to push for a top-six finish in the Premier League next season.