The iconic actress died Feb. 15 at the age of 82.
According to the star's death certificate, obtained by ET, Welch's cause of death was cardiac arrest. The document also lists Alzheimer's Disease as an underlying cause of the veteran star's death.
Welch's battle with Alzheimer's had not been publicly revealed during her lifetime. Per the certificate, the icon died at home around 2:30 a.m. and was cremated days later.
The actress' rep, Steve Sauer, previously told ET of Welch's death, "The legendary bombshell actress of film, television and stage, passed away peacefully early [Wednesday] morning after a brief illness."
Sauer added, "The 82 year-old actress burst into Hollywood in her initial roles in One Million [Years], B.C. and Fantastic Voyage. Her career spanned over 50 years starring in over 30 films and 50 television series and appearances. The Golden Globe winner, in more recent years, was involved in a very successful line of wigs. Raquel leaves behind her two children, son Damon Welch and her daughter, Tahnee Welch."
Welch first earned fame in the 1966 film Fantastic Voyage and, later that same year, catapulted into the spotlight as Loana -- donning an iconic "prehistoric" bikini -- in One Million Years B.C.
She won a Golden Globe for her performance as Constance Bonacieux in the 1973 film, The Three Musketeers. She was nominated again for a Golden Globe in 1987 for her role in Right to Die.
Welch received a star on the Hollywood Walk of Fame in 1994.
She was married four times and is survived by her two children, Tahnee and Damon Welch.
TMZ was first to report the news of Welch's death certificate.