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Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca2+ mobilizing second messenger discovered to date and has been implicated in Ca2+ signaling in human Jurkat lymphoma T cells via ryanodine receptor activation. In contrast, the role of NAADP in Ca2+ signaling or the identity of the Ca2+ stores targeted by NAADP in conventional naïve T cells has not been investigated. In the current study, we demonstrated for the first time to our knowledge the importance of NAADP in the generation of Ca2+ signals in murine conventional naïve T cells. Combining live-cell imaging methods and a pharmacological approach using the NAADP antagonist Ned-19, we addressed the impact of NAADP on the generation of Ca2+ signals evoked by TCR stimulation and the role of this signal in downstream physiological endpoints such as proliferation, cytokine production, and other responses to stimulation of murine naïve T cells. Moreover, we demonstrated that acidic stores in addition to the endoplasmic reticulum are the relevant Ca2+ stores that were sensitive to NAADP in naïve T cells.