The nematode Caenorhabditis elegans is a powerful model to study cellular stress responses. Due to its transparency and ease of genetic manipulation, C. elegans is especially suitable for fluorescence microscopy. As a result, studies of C. elegans using different fluorescent reporters have led to the discovery of key players of cellular stress response pathways, including the mitochondrial unfolded protein response (UPR<sup>mt</sup>). UPR<sup>mt</sup> is a protective retrograde signaling pathway that ensures mitochondrial homeostasis. The nuclear genes
hsp-6 and
hsp-60 encode mitochondrial chaperones and are highly expressed upon UPR<sup>mt</sup> induction. The transcriptional reporters of these genes,
hsp-6::gfp and
hsp-60::gfp, have been instrumental for monitoring this pathway in live animals. Additional tools for studying UPR<sup>mt</sup> include fusion proteins of ATFS-1 and DVE-1, ATFS-1::GFP and DVE-1::GFP, key players of the UPR<sup>mt</sup> pathway. In this protocol, we discuss advantages and limitations of currently available methods and reporters, and we provide detailed instructions on how to image and quantify reporter expression.