The period from 1000 (approx.) to 1790 can be described as the medieval period in the history of Garhwal. This period also saw the rise and fall of the Muslim and Mughal rule in the rest of India. These developments also had a bearing on the history of Garhwal.

In the early years of this period, Garhwal was ruled by numerous small chiefs or rulers amongst whom the Pala dynasty was one of the most prominent. There are a few indications of the nature of the rise to suzerainty of the Pala dynasty which in later days ruled a large part of what is now Uttarkashi, Tehri, Chamoli and Pauri districts.

It was not until the reign of Ajai Pal (1358 to 1370) that the Palas acquired the hegemony over a large part of Garhwal by subjugating the Khasa rajas. Before this time, there were very small chiefdoms under a federation which had the protection of the powerful kings of the plains, whose capital was near Indraprastha (Delhi).

Son Pal was the first of the rajas of Garhwal about whom there exist precise records. His headquarters were in the Bhilangana valley. Many Khasa rajas owned allegiance to him and he had sway over western Garhwal, which included the pilgrim route to Gangotri. A prince of the Panwar house of Dharanagar came on a pilgrimage to holy places in the hills and visited Raja Som Pal on his way. The raja had no son and was so pleased with the young prince that he gave his daughter in marriage and a part of Chandpur pargana as dowry. This young prince was Kadil Pal.
Ajai Pal, a descendant of Kadil Pal, brought the capital from Chandpur to Devalgarh in the 14th century and is considered to be the king who attempted to bring the scattered states of Garhwal under one power or authority.

Bahadur or Balbahadra Sah was the first king who dropped the surname 'Pal' and adopted the title of 'Sah', which is still borne by the descendants of the erstwhile state of Tehri. According to the legend, Emperor Bahadur Khan Lodi of Delhi came to Garhwal for a holiday. He was so pleased with the reception accorded to him by the Raja of Tehri that he conferred the title 'Sah' upon the Raja. This visit may have taken place in the year 1353.
Man Sah, one of the descendants of Bahadur Sah attained prominence around 1537. He was succeeded by Sama Sah and then by Dularam Sah, who was the first raja to come in direct contact with the Chand kings who were gaining power in Kumaon during that period.

There was a brief but decisive war with the Chands of Kumaon during the reign of Dularam Sah in Garhwal and Rudra Chand (1565 - 1597) in Kumaon. The latter was supreme in Kumaon and wanted to add Badhan in the Pindar valley (part of Garhwal state) to his dominion. The route to the Pindar valley lay through Someshwar and Katyur valley, which was then held by Sukhal Deo, the last reigning king of the ancient Katyuri family. Dularam Sah promised his protection if Sukhal Deo would aid him, and sending a force towards Gwaldam and one towards Ganai, occupied the passes towards Badhangarhi.

Porkhu, who was Rudra Chand’s general, proceeded with a small band of veteran warriors through Katyur to the Pindar valley. However, his supply lines were cut off by the Katyuri raja. Soon after, a Padyar Rajput killed general Porkhu near Gwaldam. The Raja of Garhwal had promised a land grant of a day's march to anyone who would bring him the head of the Kumaoni general. The Padyar Kajput carried the head of the dead general to Srinagar and received his promised reward. After this the Kumaoni soldiers fled to Kumaon.

However, Rudra Chand continued to harass the frontiers of Garhwal. He even overran the Katyur valley. Rudra Chand died in 1597 and was succeeded by his son, Lakshmi Chand. The latter, too, raided the frontier tracts of Garhwal several times but was repulsed with considerable loss.

Mahipati Sah was the ruler of Garhwal when Lakshmi Chand was at the throne in Kumaon. He changed the capital from Dewalgarh to Srinagar. He consolidated his rule over most parts of Garhwal. This hilly region became very prosperous during this period. There existed mines of copper and lead, while gold was obtained by washing the riverine sediments in the Alaknanda and Bhagirathi valleys and along the Sona river in the Patli dun valley.

In 1654-55, during the reign of Pirthi Sah, the Muslim rulers of Delhi invaded Garhwal. A force was sent under Khalil Ullah Khan, who speedily overran the Dehradun valley, but did not penetrate deep into the hills lying further north. After this, Pirthi Sah made peace with the rulers of Delhi.

The conflict with Kumaon continued even during and after the region of Pirthi Sah. The ruler of Kumaon was Baz Bahadur, who fought on the side of Khalil Ullah, when the Muslim force invaded Garhwal. He made two simultaneous attacks on Badhan in the Pindar valley and on Lohba. The frontier fort of Juniyagarh was seized in the process. He then attacked the Tibetans in the north and during this campaign, the Raja of Garhwal took advantage of his absence and attacked the Kumaoni garrisons to recover his territory. At this Baz Bahadur reacted very quickly and drove the Garhwalis back. A hasty peace was then signed at Srinagar.

The conflict with the Kumaonis continued even after the death of Pirthi Sah and Baz Bahadur. In fact, this continued for more than two hundred years. This was primarily in the form of raids and counter raids into each other's territory.

Pradip Sah, one of the most important rulers of Garhwal, came to the throne in 1717. He was able to make temporary peace with the kings of Kumaon. This period brought prosperity to both these regions. This prosperity attracted the attention of Nazib Khan, the Rohilla chief of Saharanpur, who invaded and took control of Dehradun in 1757 after feeble resistance from the Raja of Garhwal. This control continued till Khan’s death in 1770.

In 1745, the RohiIlas under Hafiz Rahmat invaded Kumaon with a large force and occupied Almora. Kalyan Chand, the ruler of Kumaon at that time, asked for assistance from the ruler of Garhwal, who after some hesitation decided to help. The forces of Garhwal and Kumaon grouped near Dwarahat but suffered a humiliating defeat at the hands of the Rohillas. The latter even threatened Srinagar and the ruler of Garhwal was forced to pay one lakh rupees on behalf of Kalyan Chand, after which the Rohillas withdrew completely from Kumaon. After this, the Chand dynasty in Kumaon became very weak and the rulers of Garhwal often interfered in the affairs of the state of Kumaon.