Van Dien was born and grew up in Milton, Florida, the son of Diane (née Morrow), a nursery school teacher, and Casper Robert Van Dien Sr., a U.S. Navy Commander and fighter pilot. There is a long military tradition in Van Dien's family. Aside from his father, his grandfather was a Marine during World War II. Van Dien is descended from an old Dutch family long settled in the New York area; his other heritage includes Swedish, French, English, and Native American.
The street on which Van Dien grew up in Ridgewood, New Jersey, Van Dien Avenue, was named after his great-great-grandfather. When Van Dien was older, his family moved to Florida, where he enrolled at the St. Petersburg campus of the Admiral Farragut Academy, graduating 3rd in command. While in the Florida prep school, Van Dien was often referred to as "Ken doll" due to his good looks, and got into many fights for that reason. Even some writers later described him as a "perfect life-sized Ken doll." After high school, Van Dien attended Florida State University in Tallahassee, where he was a member of Sigma Alpha Epsilon fraternity.
Moving to Los Angeles, Van Dien landed a number of small parts in various television series and movies. Two early breaks were recurring roles as Ty Moody on the daytime soap opera One Life to Live and the prime time drama Beverly Hills, 90210. Keen to expand his acting talents, Van Dien took a bit part in the video game, Wing Commander IV.
Van Dien starred in the 1997 James Dean biopic James Dean: Race with Destiny. Soon after, he got the breakthrough role of Johnny Rico in Paul Verhoeven's 1997 science fiction action film Starship Troopers. This directly led to his being cast as Tarzan in Tarzan and the Lost City (1998). Van Dien next played Brom von Brunt in Tim Burton's 1999 film Sleepy Hollow, a reworking of the classic Washington Irving tale.
In 2000 Van Dien appeared in Cutaway as well as Aaron Spelling's short-lived NBC prime time soap Titans with Yasmine Bleeth, John Barrowman, Perry King and Victoria Principal. He filmed several scenes as Patrick Bateman, the character that Christian Bale had played in 2000's American Psycho, in 2002's The Rules of Attraction. However, the scenes were unused in the final film.
In 2008 Van Dien returned to the role of Rico in Starship Troopers 3: Marauder, a direct-to-video sequel to Starship Troopers.
Van Dien replaced Matt Mullins as Johnny Cage for the second season of the YouTube webseries Mortal Kombat: Legacy.
In 2013 Van Dien played the part in Assumed Killer in which he was a husband to woman who had retrograde amnesia, who believed him to be a serial killer.
Van Dien was married to Carrie Mitchum (granddaughter of Robert Mitchum) from 1993 to 1997. They have two children, Casper "Cappy" Robert Van Dien III and actress Caroline Dorothy Grace "Gracie" Van Dien, of whom Van Dien holds full custody. Van Dien had co-starred with Robert Mitchum in James Dean: Race with Destiny. Grace Van Dien is known for starring in the Netflix series Greenhouse Academy.
Van Dien met actress Catherine Oxenberg, who is 7 years his senior, during the filming of the 1999 TV movie The Collectors, and they soon worked together again in the 1999 thriller The Omega Code. On May 8, 1999 they married in Las Vegas, Nevada. In 2005 the couple appeared in their own reality series, I Married a Princess, which aired on the Lifetime Television channel in the United States, LIVINGtv in the United Kingdom and Lifestyle You in Australia; Oxenberg's mother is Princess Elizabeth of Yugoslavia. During the 2006-2007 TV season, Van Dien and Oxenberg co-starred in the American drama series Watch Over Me on MyNetworkTV. Van Dien and Oxenberg have two daughters, born in 2001 and 2003.
Oxenberg and Van Dien are celebrity ambassadors for the non-profit organization Childhelp.
Van Dien filed for divorce from Oxenberg in 2015.