Nadal, a national hero in Spain who spoke out before the referendum to condemn it, was visibly moved as he addressed a press conference in Beijing.
Sunday's plebiscite was organised under the threat of reprisals and criminal charges but thousands of Catalans stood in defiance of the central government in Madrid.
Nadal, a national hero in Spain who spoke out before the referendum to condemn it, was visibly moved as he addressed a press conference in Beijing, where he starts his assault on the China Open on Tuesday.
The 31-year-old, who grew up and lives on the Balearic island of Mallorca but is also a Catalan speaker, said he had watched events of the weekend unfold "with concern and sadness".
Dozens of people were injured and Nadal said: "I want to cry when I see a country where we have known how to co-exist and be a good example to the rest of the world get to a situation like this.
"I think the image we have presented to the world is negative."
The 16-time Grand Slam winner added: "It was a sad moment, my heart sank all day.
"Moreover, from here, at a distance, you experience it differently.
"I have spent many parts of my life in Catalonia, important moments, and to see society so radicalised surprises and disheartens me."
Catalonia's leader Carles Puigdemont says the region has won the right to break away from Spain after 90 percent of voters chose independence.