Singh was still a minor when he became Maharaja and a council of regency ran the Patiala State government until he came of age in 1870.

[1][2] In the 1870 Birthday Honours, Singh was appointed a Knight Grand Commander of the Order of the Star of India.

[4] In 1873, during the Bihar famine of 1873–1874, he donated 10 lakh rupees to the British Raj government to help famine-stricken people in Bengal.

[6] During his reign, numerous artists and painters from Rajasthan and Himachal Pradesh would work at his court in Patiala.

[9] His Highness Farzand-i-Khas-i-Daulat-i-Inglishia, Mansur-i-Zaman, Amir ul-Umara, Maharajadhiraja Raj Rajeshwar, Sri Maharaja-i-Rajgan, Maharaja Sir Mahendra Singh, Mahendra Bahadur, Yadu Vansha Vatans Bhatti Kul Bushan, Maharaja of Patiala, GCSI.