The post was lying vacant since March when senior Congress MLA Tarvinder Singh Marwah had resigned following allegations that he got his daughter admitted in a Delhi University college using fake documents.
Dikshit had appointed Sharma on Tuesday.
Speaker of Delhi Assembly Yoganand Shastri, all the Cabinet Ministers, a number of MLAs and senior officials were present at the oath taking ceremony held at Delhi Secretariat.
Speaking on the occasion, Dikshit hoped that Sharma would be able to function his duties efficiently as her Parliamentary Secretary. "He is an experienced and committed legislator," she said.
Sharma in turn said he would strive hard for victory of Congress for fourth time in next year's assembly polls.
The Uttam Nagar MLA also holds the post of Chairman of Public Undertakings Committee. He is also spokesperson of the Congress Legislature Party.
There has been speculation that Dikshit is also planning to effect a reshuffle of her Cabinet soon.