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An inexpensive and simple three-dimensional (3D) printed spectrophotometer that interfaces with smartphone cameras for visualizing and measuring visible wavelength absorbance and analyte quantitation is reported. A conventional spectroscope inspired the spectrophotometer design to maximize visual engagement for educational purposes and functions as a single-beam visible spectrophotometer capable of precise calibration, standard curve generation, and quantitative analysis of real-life samples. Spectrophotometer calibration results using a four-point, red-green-blue coordinate-to-wavelength conversion demonstrate that the 3D-printed device exhibits a linear 5.0 nm/mm dispersion over the 400–700 nm range. Quantitative analysis validation using a smartphone camera and Open Source software (ImageJ) analysis for tartrazine determination demonstrate the molar absorptivity for the external standard tartrazine was significantly lower compared to the literature and commercial instrumentation (0.0062 μM^–1cm^–1versus 0.0216 μM^–1cm^–1for the commercial instrument). Still, the accuracy of the device was within the linear range is remarkable, as tartrazine determination in a real-life sample (Mello Yello soft drink) was found to be not statistically different compared to the result obtained on a commercial spectrophotometer (10.6 μM versus 10.5 μM, n = 5, p > 0.05). The device design and computer-aided drafting files are available publicly for Open Access replication and modification, with considerable promise for expanded capabilities and applications beyond visible spectroscopy and educational purposes.