Tectonic earthquakes from the volcano had been detected since early August 2017, and volcanic activity intensified for several weeks before decreasing significantly in late October.

Agung erupted in 1843[2] as reported by Heinrich Zollinger: After having been dormant for a long time, this year the mountain began to be alive again.

This concern was the primary reason behind their decision to evacuate more than 100,000 people in response to the surge in local tectonic activity in the latter half of 2017.

[15][16] A small phreatic eruption was reported at 09:05 on 21 November (UTC), with the top of the ash cloud reaching 3,842 metres (12,605 ft) above sea level.

[20] The eruption plume rose 1.5–4 kilometres (4,900–13,100 ft; 1,500–4,000 m) above the summit crater, drifting towards the south[20] and dusting the surroundings with a thin layer of dark ash, leading some airlines to cancel flights bound for Australia[20] and New Zealand.

[25] Sunday 26 November's eruption continued at a constant rate,[26] and lahars were reported in the Selat district south of the volcano.

[26] Reductions in eruption intensity and wind dispersal of the ash cloud led authorities to reopen Ngurah Rai International Airport at 07:00 (UTC).

[29] The volcano erupted once again on 11 January, sending plumes of smoke and ash, while Indonesia's Bali international airport was declared safe, operating normally.

On 28 June, water vapour and volcanic ash emission were detected from Mount Agung up to two kilometres (6,600 ft; 2,000 m) into the air.

[35] Several villages in Bali were covered in a thin layer of ash, but no smoke or lava was detected coming from the volcano and no evacuation has been ordered.

[36] On 22 February, volcanic ash plume that rose up to estimated 14,000 feet (4,300 m) altitude or flight level 140 Explosive activity continues on 8 March or the day after Nyepi, with a volcanic ash plume that rose up to estimated 12,000 feet (3,700 m) altitude or flight level 120 and is moving at 10 knots (19 km/h; 12 mph) in south east direction.

In late May 2019 an eruption spewed lava and rocks over about 3 kilometres (9,800 ft; 3,000 m), with some ash fall on nearby villages and temporarily interrupting international flights.

A Vulcanian eruption ejected much incandescent material to distances of at least 700 metres (2,300 ft) from the crater and generated an ash plume that rose to 30,000 feet (9,100 m) altitude and drifting south over Denpasar.

Ngurah Rai International Airport, located at the southern tip of the island and southwest of the volcano, closed on 27 November.