The 47-year-old, who also owns the Bangladeshi-origin eatery, had denied causing actual bodily harm and said he had acted in self-defence because Evans was being aggressive.
A jury at Merthyr Crown Court agreed with his version of events and declared him not guilty today.
"I am happy and relieved. I was very confident that the British system would find the right answer, Islam said after the verdict.
The prosecution case was that the curry house owner had grabbed a handful of chilli powder and threw it in the face of David Evans, thereby causing him "difficulties with his eyes".
The incident occurred over a dispute about the quality of the chicken served to Evans and his wife, who were dining at the Prince of Bengal on January 22, 2017.
Describing the chicken, Evan said: It tasted rubbery and like paraffin. It was shiny. I go to lots of Indian restaurants and I have never tasted food like that before.
Islam told the court that he was "very frightened" as the couple shouted at him and as he walked away from the table he could hear being followed.
I ran to get the chilli powder because I wanted to get it before he grabbed me, he claimed.
Evans doubled up in pain and was taken to hospital where a saline drip was used to clean his eyes and he was found to have suffered burns where the spice landed on him. Islam was arrested later the same evening.
Jurors were shown CCTV footage from the evening as the defence challenged the couples sequence of events.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)