Gilardino was overlooked for the Azzurri's final 23-man squad for the finals in Brazil, with Alessio Cerci, Lorenzo Insigne, Ciro Immobile and Antonio Cassano selected alongside Mario Balotelli as striking options.
The 32-year-old, who played under Prandelli at Parma, admits he felt he deserved better treatment from his former coach after being snubbed from his plans for tournament, which ended in the group stage for the Azzurri.
"I expected a phone call from him, I thought we had a different relationship to that after six or seven years together," Gilardino told Sky.
"I am certainly disappointed by his behaviour."
However, Gilardino insisted he does not resent Prandelli for his lack of a personal touch and praised his former coach for his influence on his development as a forward.
"It didn't happen but I don't bear a grudge, my opinions of him remain the same," he added.
"At Parma he transformed me into a footballer, he showed me how to move in the penalty area and be decisive."
Gilardino recently signed for Chinese side Guangzhou Evergrande, while Prandelli took over at Galatasaray after stepping down from his post as Italy boss.