Lanthanide-based nanocrystals possess three unique physical properties that make them attractive for facilitating photoreactions, namely photon upconversion luminescence, Lewis acid catalytic activity and photothermal properties. When co-doped with a suitable sensitizer and activator lanthanide ions, rare-earth fluoride nanocrystals upconvert near-infrared light to higher energy photons that can be used to excite photosensitizers that absorb ultraviolet and visible light in photocatalytic and photopolymerization reactions. Surface lanthanide ions on nanocrystals also have the propensity to behave as Lewis acid (LA) catalytic sites. In addition, NIR-light excited lanthanides such as Nd3+ undergo cross-relaxation interaction with neighbouring ground-state ions followed by non-radiative decay to generate heat (i.e., photothermal) which enhances the rate of chemical reactions. In this perspective, we provide a survey of the recent progress in the use of lanthanide-based nanocrystals as upconverting nanolamps, LA catalysts and photothermal nanoheaters in driving synthetic and polymerization reactions, and the challenges that need to be further addressed in order for this vibrant research area to develop and grow.