A dual-wavelength metalens enables epifluorescence detection from single molecules. This study presents a dielectric metalens with submicrometer thickness that replaces traditional objective lenses to excite and collect light from fluorescent molecules. The metalens, made of hydrogen-doped amorphous silicon (aSi:H) meta-atoms, achieves high numerical aperture (NA = 0.6), high focusing efficiency, and dual-wavelength operation. It enables fluorescence correlation spectroscopy (FCS) with a single Alexa 647 molecule in the focal volume and real-time monitoring of individual fluorescent nanoparticle transitions. The metalens provides high sensitivity, allowing detection of hydrodynamic diameters ranging from a few to hundreds of nanometers. This advancement enables the miniaturization of single-molecule detection systems for portable devices. The metalens operates in one-photon epifluorescence mode without an objective lens, focusing laser light through a thin glass slide inside a fluorescent solution. The confocal configuration and nanosecond signal time gating allow detection of fluorescence from the focal volume with minimal background noise. The metalens is fabricated using electron-beam lithography and has a diameter of 500 μm and a focal length of 330 μm. It achieves high transmittance and conversion efficiency at both 635 nm and 670 nm wavelengths. The metalens enables the detection of single molecules and nanoparticles with high sensitivity. It can distinguish nanoparticle sizes far below the diffraction limit, where spatial analytical methods of microplastic are typically flawed. The metalens can detect single molecules and nanoparticles in aqueous solutions, with the ability to identify their hydrodynamic diameters. The metalens also allows real-time monitoring of quantum dots and stained nanoparticles, providing information on their diffusion times and brightness. The metalens performance is compared with conventional optics, showing that it can achieve similar single molecule sensitivity with a single layer of dielectric nanofins, while being miniaturized by around 2 orders of magnitude in all dimensions. The dual-wavelength operation of the metalens enables efficient collection of diffusing molecules, making it suitable for single molecule sensing and dynamics studies. The metalens can be integrated with available miniaturized microscope solutions, such as smartphone microscopes and 3D-printed FCS platforms, making it a viable candidate for integrating single molecule on-chip sensors for point-of-care testing.A dual-wavelength metalens enables epifluorescence detection from single molecules. This study presents a dielectric metalens with submicrometer thickness that replaces traditional objective lenses to excite and collect light from fluorescent molecules. The metalens, made of hydrogen-doped amorphous silicon (aSi:H) meta-atoms, achieves high numerical aperture (NA = 0.6), high focusing efficiency, and dual-wavelength operation. It enables fluorescence correlation spectroscopy (FCS) with a single Alexa 647 molecule in the focal volume and real-time monitoring of individual fluorescent nanoparticle transitions. The metalens provides high sensitivity, allowing detection of hydrodynamic diameters ranging from a few to hundreds of nanometers. This advancement enables the miniaturization of single-molecule detection systems for portable devices. The metalens operates in one-photon epifluorescence mode without an objective lens, focusing laser light through a thin glass slide inside a fluorescent solution. The confocal configuration and nanosecond signal time gating allow detection of fluorescence from the focal volume with minimal background noise. The metalens is fabricated using electron-beam lithography and has a diameter of 500 μm and a focal length of 330 μm. It achieves high transmittance and conversion efficiency at both 635 nm and 670 nm wavelengths. The metalens enables the detection of single molecules and nanoparticles with high sensitivity. It can distinguish nanoparticle sizes far below the diffraction limit, where spatial analytical methods of microplastic are typically flawed. The metalens can detect single molecules and nanoparticles in aqueous solutions, with the ability to identify their hydrodynamic diameters. The metalens also allows real-time monitoring of quantum dots and stained nanoparticles, providing information on their diffusion times and brightness. The metalens performance is compared with conventional optics, showing that it can achieve similar single molecule sensitivity with a single layer of dielectric nanofins, while being miniaturized by around 2 orders of magnitude in all dimensions. The dual-wavelength operation of the metalens enables efficient collection of diffusing molecules, making it suitable for single molecule sensing and dynamics studies. The metalens can be integrated with available miniaturized microscope solutions, such as smartphone microscopes and 3D-printed FCS platforms, making it a viable candidate for integrating single molecule on-chip sensors for point-of-care testing.