Joshua Davies, 19, was injured after falling on to rocks in Pontypridd, Rhondda Cynon Taff, last year.
Kurtis Lawrence, 18, and two boys, aged 16 and 15, who cannot be named, denied throwing stones aimed at Mr Davies.
They were found not guilty of causing grievous bodily harm with intent and of inflicting grievous bodily harm by a jury at Cardiff Crown Court.
Three teenagers have been cleared of all charges relating to a man who was paralysed when he fell from a bridge.