Venezuelan Professional Baseball League vice president Domingo Alvarez says the captors have not made contact with Ramos' family. He said it's the first time a Major League Baseball player has been abducted in the country, though relatives of other players have been held for ransom in the past.
Ramos, a 24-year-old who just finished his rookie season, was taken away in an SUV by four armed men in Santa Ines in central Carabobo state, the spokeswoman for his Venezuelan League team, the Aragua Tigers, said on her official Twitter account.
"This is sad, worrisome and true that Wilson Ramos has been kidnapped," Katherine Vilera tweeted.
She said Ramos was taken at 6:45 p.m. local time at his home in the region 95 miles west of Caracas. She said police were notified.
A person close to Ramos' family, who asked not to be quoted by name out of safety concerns, said the catcher was at home with his father and brothers when several men "entered the house and took him away."
Drew Storen, a relief pitcher for the Nationals, tweeted his concerns: "Extremely upsetting news about Ramo. Thoughts and prayers with him. Scary situation."
Spokesmen for the Nationals did not respond immediately to phone and email messages Wednesday night.
Ramos' agent, Diego Bentz, had no comment when reached by ESPN.com.
Ramos is considered one of the Nationals' key young players as they try to become a contender in the National League East. As a rookie in 2011, he hit .267 with 15 home runs and 52 RBIs in 113 games. He also threw out 19 of 67 runners attempting to steal a base, a 28 percent success rate that ranked third among qualifying catchers in the National League.
Venezuela police last year said 618 kidnappings were reported in 2009, and the numbers have grown rapidly in recent years.
In November 2009, the then 56-year-old mother of Victor Zambrano, who retired after pitching for four teams during a seven-year major league career, was rescued in a "commando-style operation" after a three-day kidnapping ordeal.
Zambrano's mother was abducted nine days after the former pitcher's cousin, Richard Mendez Zambrano, had been kidnapped and later killed.
The mother of former player Ugueth Urbina, who was a two-time All-Star pitcher while playing for six teams, spent more than five months in captivity until she was rescued in early 2005.
Around the same time, the mothers of five Brazilian soccer players were abducted in Brazil, including those of star strikers Robinho and Luis Fabiano.
Information from The Associated Press was used in this report.