Despite now owning a majority of the club, Ronaldo has agreed that president Carlos Suarez will remain in his position, while the World Cup winner will take on the role of president of the board of directors.
The club's new majority owner was unveiled on Monday at a press conference where he outlined his plans for the future of the club.
"We want to grow and reach where our will allows us," Ronaldo said. "I will use four words to define our politics: Competitiveness, Transparency, Revolution and Social. I assure you that you will find me as a lover of Castilla-Leon, Valladolid and Real Valladolid."
Suarez is delighted to welcome Ronaldo on board, confirming that negotiations took just over a month to finalise. The club president believes the addition of the former Real Madrid striker will help put Valladolid "on the map" while also indicating that it was not merely a financial decision to sell to the Brazilian.
"The deal was closed on Wednesday," Suarez announced. "Ronaldo acquired 51% of the shares in a personal capacity. It was at the end of July when we started talking.
"It was not an economic issue, but now Valladolid can play in other leagues, Ronaldo puts us on the map now. I thought it was the best for the club, and that's what I bet, you'll see that it's the ideal option for Valladolid."
Since retiring from football in 2011, the three-time FIFA World Player of the Year winner, Ronaldo took an active interest in other sports and owning teams, including motorsport group A1 Team Brazil and sports marketing firm 9INE.
He also owns shares in North American Soccer League club Fort Lauderdale Strikers and founded the Ronaldo Academy, a youth football school in the United States and China.
During his playing career, he played over 500 games for teams such as PSV, Barcelona, Real Madrid and both Milan clubs. He also scored 62 goals in 98 appearances for Brazil, winning the World Cup in 1994 and 2002.