Nikki's diary is Nikki's most valuable possession as stated by Nikki numerous times in her diary. It was bought by her mom in the first book as a back to school present. When Nikki first recieved this diary, she was deeply disappointed because she wanted an iPhone. She has also said that, in the first book she was never going to write in the diary again, but she later said that she meant it at the time. In book 3 1/2, Nikki's diary has gone missing, later finding out that Brianna took it to her school for show and tell. Nikki's diary is mostly filled with doodles, comic strips and her innermost thoughts and feelings.