Fast and reasonable low‐scale (200 nmol) syringe‐made synthesis of 15N‐labeled oligonucleotides representing DNA trinucleotide codons is communicated. All codons were prepared by solid‐phase controlled pore glass synthesis column technique via the phosphoramidite method. Twenty‐four labeled oligonucleotides covering the DNA genetic code alphabet were prepared using commercially available reagents and affordable equipment in a reasonably short period of time, with acceptable yields and purity for direct applications in mass spectrometry. A controlled pore glass (CPG)‐supported oligonucleotide synthesis of DNA trinucleotide codons containing various combinations of 15N‐labeled nucleic bases A, G, C, and T is reported. The cost‐effective protocol uses a simple commercially available equipment and an optimized amount of valuable 15N‐labeled phosphoramidite used for the coupling step.