 On 30 June 1835, he was appointed secretary of the special embassy sent to Tehran under Henry Ellis to congratulate Mohammad Shah Qajar on his accession to the Persian throne.McNeill received permission to wear the Persian Order of the Lion and the Sun of the first class, and on his return home in the spring of 1836, he anonymously published a startling anti-Russian pamphlet, "Progress and Present Position of Russia in the East".From 1836 to 1844, McNeill was any envoy to Persia.