The viticulture industry is facing challenges in protecting grapevines against fungal pathogens, while minimising their impact on the environment. Modern wine production has been highly dependent on the use of fungicides to control grapevine diseases such as grey mould, downy mildew, and grapevine trunk diseases. The intensive use of fungicides is causing environmental contamination with pesticide residues and development of fungicide-resistant in fungal pathogens. The application of nanoformulations in viticulture is garnering interest among winegrowers motivated to seek novel technologies that provide adequate crop protection while minimising the environmental impacts. There is a current need to determine the overall risks and benefits of existing nanotechnologies when applied to viticulture and their potential effect on the environment. This critical review aims to evaluate existing nanoformulations (nanocarrier + active ingredients) according to nanocarrier type, functionality, and efficacy against specific fungal pathogens of grapevines. Prospective nanocarriers for conventional fungicides are nanoparticles made from mesoporous silica, chitosan, and polymeric polysaccharides. For the delivery of RNAi-based fungicides, carbon quantum dots, chitosan, silica, and Bioclay are promising technologies for the delivery of double-stranded RNA in plants. Nanocarriers showed a wide range of surface modification that can determine the controlled release of loaded pesticides and improve stability in field conditions compared to commercial formulations. Most of the studies reviewed were in the early stages of development and often lack field testing; used non-standardised characterisation methods; and provided insufficient information on the efficacy of nanoformulations versus commercial-grade equivalents. Current barriers in the wide use of nanotechnologies in viticulture include regulatory requirements and the negative perception towards nano-pesticides. Future research into nanoformulations will require robust characterisation to provide adequate information to surpass these barriers. A problem-oriented approach is needed in developing nanotechnologies where nanocarriers are developed for specific uses prior to formulation instead of the inverse approach.