Unidentified attackers opened fire on him on Monday in Culiacan city in the north-western state of Sinaloa, where he lived and worked.
Valdez wrote several books about Mexico's drug wars, including a volume previous year on narco-periodismo, or narco-journalism.
But if Valdez's case is anything like that of the many other reporters who have been murdered in Mexico recently, there's a good chance his killers will never be punished.
In a report this month, CPJ noted that most killings of journalists go unpunished in Mexico. "I don't want to be asked, 'What were you doing in the face of so much death. why didn't you say what was going on?'" The outlet said that he was driving close to the offices of the publication in Culiacán when his vehicle was intercepted and shot him dead.
Valdez knew well the dangers of reporting on cartel activity, telling the Committee to Protect Journalists (CPJ) a few weeks before his murder that he was concerned for his safety. "You have to fight to change things'".
Journalists wrote "they are killing us" in large letters at the foot of the Angel of Independence monument in central Mexico City and flashed pictures of dead reporters to passing cars.
"And for that same reason, he and his magazine and his co-workers were always under threat of violence", Hootson said.
Over a almost 30-year career, Valdez became one of the most renowned journalists in Sinaloa.
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The cartel is believed to be responsible for an estimated 25% of all illegal drugs that enter the U.S. via Mexico. The young man died instantly, while his mother died on the way to the hospital, according to Tabasco Hoy, although the attorney general of Jalisco has not confirmed her death. The state of Sinaloa is the base of Joaquin "El Chapo" Guzman's Sinaloa Cartel, and has seen a surge in violence since his arrest, as rival members of his gang vie to wrestle control.
Javier Valdez Cardenas, who won the Committee to Protect Journalists' global press freedom award in 2011, died when gunmen opened fire on his vehicle around noon.
Journalists targeted in Mexico are most often local reporters in places where the rule of law is tenuous, but there have also been killings of journalists with national profiles such as Valdez and Regina Martinez Perez, who was slain in 2012.
He was known for his smile and white Panama hat.
"Being a journalist is like being on a black list", he wrote in a recent book about drug gangs and the media.
At least 104 journalists have been murdered in Mexico since 2000, according to the New York Times.
In 2011, the CPJ gave Valdez an International Press Freedom Award for his coverage of the victims of the drug war.