Store-operated Ca²⁺ channels in the plasma membrane (PM) are activated by the depletion of Ca²⁺ from the endoplasmic reticulum (ER) and constitute a widespread and highly conserved Ca²⁺ influx pathway. The best understood store-operated channel is the CRAC channel, which is essential for immune cell function. After store emptying, the ER Ca²⁺ sensor STIM1 forms multimers, which then migrate to ER-PM junctions where they activate the CRAC channel Orai1. Movement of an intracellular protein to such specialised sites where it gates an ion channel is without precedence but the fundamental question of how STIM1 migrates remains unresolved. Here, we will describe recent results that suggest mitochondria influence trafficking of STIM1 to ER-PM junctions. When open, Ca²⁺ entry through CRAC channels feeds back to inhibit further Ca²⁺ influx. Through their ability to buffer cytoplasmic Ca²⁺, mitochondria reduce Ca²⁺-dependent inactivation and thus sustain Ca²⁺ influx. This is important for maintaining slow Ca²⁺-dependent responses including secretion of paracrine signals and gene expression.