The 40-year-old man has been arrested on suspicion of conspiracy to cause grievous bodily harm.
Pouria Zeraati, who works for London-based dissident broadcaster Iran International, was injured as he approached his car in Queensmere Road, Wimbledon on March 29, 2024.
The suspect was arrested in Cricklewood on Tuesday, January 7, and questioned at a police station in west London before being bailed until April.
Two Romanian nationals have already been charged with wounding and wounding with intent to cause GBH in relation to the stabbing.
Nandito Badea, 19, and George Stana, 23, were arrested at Heathrow Airport after being extradited to the UK from Romania.
They are due to appear at the Old Bailey on January 17.
