Novel techniques such as ultrashort pulsed laser technology to produce in situ bio-conjugated nanoparticles (NP) as biomarkers for optical imaging and intervention hold great potential to observe dynamic processes in gametes and embryos without affecting their developmental potential. With regard to toxicology, current preliminary evidence is mainly based on specific cell lines and suggests low toxicity for gold NP (GNP), but a higher toxicity for silver NP (SNP), which also possess a considerable antibacterial effect. Little is known about their impact on sensitive biological systems as early mammalian embryos. The present study investigated the potential toxicity of GNP and SNP in murine embryos for the first time. Since the NP were laser-generated, they formed a stable dispersion in water without the need of surface coating, which might have caused additional toxic effects. Approximately 10 pL of a NP díspersion (average NP diameter of 15 nm) containing 50 μg mL^-1 of either GNP or SNP were injected into 1 blastomere of 2-cell-stage embryos (n = 93 or 75, respectively), derived from superovulated NMRI mice. Embryos injected with water alone (n = 79) served as controls. Untreated embryos (n = 92) were run as a handling control. Successful NP injection was confirmed using laser scanning confocal microscopy. After treatment, embryos were cultured for 72 h at 37°C and 5% CO₂ in KSOM plus 1% BSA. Embryo development was assessed on a daily basis. No abnormal development was observed. The handling controls reached a blastocyst rate of 77.2%. A total of 66.2% of the water-injected embryos developed to blastocysts, compared to 62.4% and 56.0% after injection of GNP and SNP, respectively. Neither 1-way ANOVA nor an additional chi-square test indicated significant differences between treatment groups. In conclusion, these preliminary data indicate that intracytoplasmatic injection of GNP and SNP had no significant impact on embryo development. Further tests, including qRT-PCR of development-relevant genes in blastocysts and transfer of injected embryos into recipient animals to study potential long-term effects, are underway to gain a better understanding of GNP and SNP embryo toxicology.