Individual water-in-oil-in-water (W-1/O/W-2) double-emulsion globules loaded with fluorescently labeled bovine serum albumin (FITC-BSA) were optically monitored within cylindrical capillaries during freeze-thaw cycling. Coalescence of internal aqueous droplets (W-1) and external aqueous phase (W-2), termed external coalescence, was not observed before or during freezing of the oil phase (O). On the other hand, this instability mechanism was readily promoted during thawing. This realization confirms the previously suggested potential of W-1/O/W-2 double emulsions to trigger release upon oil thawing(1) and demonstrates that it is a direct result of globule breakage through external coalescence. The presented results also identified a threshold in the relative W-1 droplet size above which instability occurred, while smaller droplets remained unperturbed and therefore indicate that optimization of the delivery can be achieved by tuning the size of W-1 droplets. In addition, we propose a possible explanation for the occurrence of instability during oil thawing and its dependence on the size of W-1 droplets. Because this alternative globule-breakage mechanism simply uses temperature increase (solid-to-liquid-phase transition) as external stimulus, W-1/O/W-2 double-emulsion delivery systems can be easily tailored by choosing an oil phase with the appropriate phase-transition temperature.