Taking to Twitter, the 26-year-old said people of Bihar will reap fruits of the "trust shown in youth".
"No one should try judging a book by its cover. Potential, like sweet nectar and bitter medicine, takes time to show its real benefit," he said in a tweet.
In another message on the micro blogging site Twitter, he said, "Cynic, biased ones with vested interest will always be dismissive but stakeholders-people of Bihar-will reap fruits -- trust shown in youth."
"Rest assured that vigor & liveliness of youth in Bihar cabinet will be ably guided n utilized by tested CM, for the welfare of ppl of Bihar," the new Bihar Deputy CM tweeted.
"I will leave no stone unturned for development & to increase the value of Brand Bihar,so that @NitishKumar can be proud of me as his deputy," he said.
Former BJP MP and cricketer Navjot Singh Sidhu had mockingly said on twitter that "Bihar is ready to get a best government of era. From SuMo (Sushil Modi) to Tejaswi Yadav Bihar will grow more rapidly."
The first time MLA from Raghopur, Tejaswi who is younger son of RJD chief Lalu Prasad has been named as Deputy chief minister in the Grand Alliance government in Bihar.
The number two position going to him and not the more experienced leaders of RJD has triggered a barrage of criticism especially in social media.
Being the biggest constituent of secular alliance with 80 MLAs, RJD supremo Lalu Prasad managed to win number two and three positions in the cabinet for his sons Tejaswi and Tej Pratap respectively.
Tejaswi and Tej Pratap arrived together for the first meeting of the state cabinet on Saturday at state secretariate.
Emerging from the meeting, Tejaswi told reporters, "Whatever responsibilty has been entrusted to us we will fullfill it without any interest."
"We will try to stand true on the expectations of the public in taking Bihar forward on the path of development," Tejaswi, who was flanked by Tej Pratap, said.
"People have selected us. This duty is not for fun but for work. We will work hard to ensure development for all irrespective of caste and religion," the new Bihar deputy chief minister said.
When queried on his lack of experience, Tejaswi said, "Nitishji and other seniors are there to guide us."
Asked if Nitish Kumar gave any specific direction to him, Tejaswi Yadav said on Saturday's cabinet meet was to convene the assembly session.
Tej Pratap, who flanked his younger brother, also said they would work hard to fulfil the expectations of the people.