A Queensland firefighter who choked a teenage boy he claims was bullying his stepdaughter has a message for any would-be parent vigilantes: "Just don't do it".

Mark David Bladen pleaded guilty in Brisbane Magistrates Court on Tuesday to one count of assault occasioning bodily harm at a skate park at The Gap, in Brisbane's west on March 3.

Mark David Bladen pleaded guilty to one count of assault occasioning bodily harm after he attacked a 14-year-old boy over allegations he bullied his step-daughter. Credit:Seven News.

He was sentenced to $1000 with no conviction recorded after the court heard he had an exemplary history, including a commendation for his work in Rockhampton in February 2015 following Cyclone Marcia.

The court heard he told police he just "snapped" when he attacked the 14-year-old boy, who he claims had been bullying his stepdaughter for months so she was too scared to go to school.