The area around Tohana used to be a desert land until the Bhakhra Nangal sub-branch Canal brought a source of irrigation for the town and neighboring villages. After this, Tohana developed into a major agricultural hub.
A channel of the mythological river Sarasvati River represented by modern day river Ghaggar crossed the area of Tohana. Aryans, at first settled on the banks of the rivers Saraswati and Drishadvati, and in the course of their expansion, covered a wide area of Hissar and Fatehabad. The area was probably included in the kingdom of Pandavas and their successors. Panini mentions quite a few towns of the region- Aisukari, Taushayana (Tohana) and Rori which have been identified with Hissar, Tohana and Rori, respectively.
The early 11th century saw the Ghaznavid inroads in this area. Sultan Masud led the expeditions towards Agroha. The Chauhans seem to have taken special measures for protecting the area against Muslim incursions. The area of Agroha passed on to the Muslim rule after the defeat of Prithvi Raj III in the Second Battle of Tarain (1192). After the Battle of Tarain, Sultan Shihab-ud-Din Muhammad Ghuri placed one of his ablest generals in the Indian campaigns. But it appears that any meaningful control could not be established. Seizing the opportunity, a Rajput clan, Jatus, believed to be an offshoot of Tomaras, widely extended their power in Fatehabad area including Agroha. Firuz (1351-1388) shot these areas into prominence. The ruler came to have somewhat unusual fancy for the tract (Hissar). It is a great credit to him that he established new towns of Fatehabad and Hissar and built two canals; one taking off from Ghaggar at Phulad and following the course of Joiya up to the town of Fatehabad. After the death of Firuz (1388), chaos and confusion spread all round . The situation deteriorated still further when Timur invaded in 1398. During his marching, Timur invested Fatehabad which was captured without any opposition from the inhabitants. Lastly, the invader reached Tohana but he could not set-up his permanent rule over the area. He soon left for Samana after looting these areas.
By 1760, the areas became the scene of a sort of triangular struggle between the sturdy Sikhs of north-east, marauding Bhattis of north-west and the Muslim chiefs of the south. None of them could, however, hold the region permanently except for the Bhattis who became the masters of Fatehabad pargana. In 1774, Maharaja Amar Singh, a Bhatti chief of the Phulkian State of Patiala, along with his famous minister Dewan Nanu Mal laid seize to the stronghold of Bighar near Fatehabad which fell shortly afterwards. The Raja then took Fatehabad and Sirsa and invested Rania held by Bhattis. Tohana also was seized by the Chief of Patiala. But after a treaty of Jind in 1781, Fatehabad and Sirsa were made over to the Muslim Bhattis Nawabs and remaining territories were allowed to be retained by the Sikhs.
By 1798, Agroha and Tohana were important parganas under the control of George Thomas. When George Thomas was driven out from here by the Sikh-Maratha-French Confederacy, a French Officer Lt. Bourquian controlled these areas on behalf of Marathas . He is said to have rebuilt the towns of Tohana and Hissar. Later these areas were placed under the charge of Illias Beg, a Mughal noble of Hansi. With the treaty of Surji Anjangaon 1803, the British became the rulers of this area and Marathas were vanquished forever.
In November 1884, the Sirsa district was abolished and Sirsa tehsil after the distribution of villages was formed . In 1889, 15 villages forming a detached block known as Budhlada were transferred form Kaithal tehsil to Fatehabad tehsil. The Barwala tehsil containing139 villages was abolished with effect from January 1, 1891 and its area was distributed between three contiguous tehsils ; 13 villages going to Hansi, 24 to Hissar and 102 to Fatehabad.. By the end of 1978, the Hissar district comprised 486 villages, divided between tehsils of Fatehabad -166; Hissar-115, Hansi-119 and Tohana-86. Fatehabad came into existence as a full-fledged district with effect from 15 July1997, now having three sub-divisions, three tehsils and three sub-tehsils.