Paxton died at the age of 61 on February 25 due to complications of a surgery.
The legendary director had worked with the actor in three blockbusters - "Aliens," "True Lies" and "Titanic".
In his note, according to The Hollywood Reporter, Cameron said, "As I sit writing this, I'm looking at a 700-pound stone head of Bacchus, the party god, that Bill Paxton had delivered to my house one day.
He got it from a hotel that was being demolished in New York and just figured his pal Cameron needed a 700-pound stone head. It has been in my living room for 15 years. That's the kind of guy Bill was. An absolute original."
Cameron wrote the director-actor duo experienced many adventured together and he cherished their collective work as "Bill brought to life so many indelible characters in my films."
Towards the end, the director said, "His zany characters on-screen belied a serious, thoughtful and caring man...He leaves a void in my life that can never be filled.