Histamine receptor H1 antagonists are widely used as antihistamines for allergy conditions. The brain-penetrating antihistamines can cause sedation and some with poor-penetration do not cause sedation potential. In the present study, a new series of thieno[2,3-d][1,2,3]triazine derivatives 7a-e have been synthesized and screened for their H1 antihistaminic activity and sedation potential. Among all the screened compounds, compound 7b, 7c and 7d, show high H1 antihistaminic activity with IC50 value of 0.1 - 0.8 µM, which are comparable with that of the standard drug cetirizine. The sedative potential of the compounds was tested on albino mice using the photoactometer method. All the three compounds show less sedation potential than that of the standard drug diphenhydramine. In conclusion, the novel compounds appear with promising potential as non-sedating antihistamine agents.