Nanowires made of materials with non-centrosymmetric crystal structure are under investigation for their piezoelectric properties and suitability for next-generation self-powered nanodevices. In this work, we report a systematic study on synthesis of trigonal tellurium nanowires with well-controlled dimensions. After assembling the tellurium nanowires on the stretchable substrates, a stretchable, soft piezoelectric nanogenerator has been developed with the capability to efficiently convert mechanical stimuli into electric power. We revealed the correlation between the piezoelectric outputs from the integrated devices and the diameters of as-produced tellurium nanowires. We further studied the feasibility of using the as-fabricated piezoelectric device for biomedical applications, such as gesture recognition. This work establishes the process-structure-property-performance relationship in the piezoelectric nanogenerator that may pave way for the nanomanufacturing and practical application of piezoelectric nanomaterials.