The present invention provides novel crystalline forms of Acalabrutinib, Specific crystalline forms provided by the present invention include Acalabrutinib Form APO-I, a co-crystal of Acalabrutinib and urea; APO-II, a co-crystal of Acalabrutinib and nicotinamide; APO-III, a co-crystal of Acalabrutinib and L- sorbitol; APO-IV, a crystalline form of Acalabrutinib; and APO-V, a co-crystal of Acalabrutinib and urea.