Officers went to an address at Albany Villas in Hove on Tuesday evening, following a report of illegal activity.
A large scale commercial cannabis site was discovered inside in some 11 rooms, where 350 plants were in various stages of cultivation, confirmed police.
Two men aged 25 and 23 were arrested on suspicion of cannabis cultivation, abstracting electricity and theft of a mobile from a motor vehicle parked nearby, according to police.
The 23-year-old was also arrested on suspicion of being illegally in the UK, police said.
After being interviewed they were released on police bail until 6 July while enquiries continue.