The voting began at 7 am amidst tight security arrangement.
PM Narendra Modi took to Twitter to urge voters to come out in large numbers to exercise their franchise.
According to an Election Commission release, the voting exercise in 18 seats will end at 3 pm. Voters in Jamshedpur (East) and Jamshedpur (West) constituencies can vote until 5 pm.
Vinay Kumar Choubey, Chief Electoral Officer, Jharkhand, said: "Several of the constituencies going for this phase of polling are Naxal-affected areas. So, armed police have been deployed as part of security measures."
Out of a total of 6,066 polling stations, 949 have been declared 'critical' and 762 sensitive' in Naxal-affected areas, he said.
The CEO said that 101 polling stations have been relocated due to security reasons and free transport facility has been arranged for voters to reach these stations to exercise their franchise.
As many as 1,016 polling stations are located in towns and cities, while 5,050 are in rural areas, Choubey said.
Webcasting facilities have been made available at 1,662 polling stations.
Out of the 6,066 polling stations, there are 337 model polling stations and 94 polling stations will be overseen by women polling personnel, he added.
A total 48,25,038 voters, including 23,93,437 female and 90 third-gender voters are eligible to vote to decide the fate of 260 candidates, including 29 women nominees and 73 independents.
More than 42,000 security personnel, including central forces, have been deployed on the 20 seats spread across seven districts.
The assembly segments going for polls are: Baharagora, Ghatsila (ST), Potka (ST), Jugsalai (SC), Jamshedpur (East), Jamshedpur (West), Seraikela (ST), Chaibasa (ST), Majhgaon (ST), Jaganathpur (ST), Manoharpur (ST), Chakradharpur (ST), Kharsawan (ST), Tamar (ST), Torpa (ST), Khunti (ST), Mandar (ST), Sisai (ST), Simdega (ST) and Kolebira (ST).
BJP leader and Chief Minister Raghubar Das is facing challenge from his former cabinet colleague and independent candidate Saryu Roy from Jamshedpur (East) seat.
Jharkhand Assembly Speaker Dinesh Oraon is contesting from Sisai on a BJP ticket, while BJP candidate and Rural Development Minister Neelkanth Singh Munda is contesting from Khunti.
The BJP's state unit president Laxman Gilua, who lost the Lok Sabha elections from Singhbhum seat, is contesting from Chakradharpur.
The AJSU party candidate and Jharkhand Water Resources Minister Ramchandra Sahis is contesting from Jugsalai.
Former Jharkhand Pradesh Congress Committee president Pradeep Kumar Balmachu, who joined the AJSU party recently, is contesting from Ghatsila.
JDU state president Salkhan Murmu is contesting from Majhgaon.
JVM-P candidate and former HRD minister Bandhu Tirkey is contesting from Mandar against former MLA Deb Kumar Dhan of the BJP.
The BJP is contesting in all the twenty constituencies in the second phase while the opposition alliance of Jharkhand Mukti Morcha (JMM) and the Congress is contesting in 14 and six seats respectively.
The RJD, which has got a total seven seats as per the seat-sharing formula of the three opposition parties, has no candidate in this round.
NDA ally AJSU party, which is contesting the assembly elections on its own for the first time since the creation of the state, has fielded candidates from 12 constituencies in this phase.
The Jharkhand Vikas Morcha (Prajatantrik) has nominated leaders in all the 20 seats while the Bahujan Samaj Party has fielded in 14 segments.
The CPI is contesting in two seats while the CPI-M is contesting in one and NCP in two.
Six candidates of the All India Trinamool Congress are also in the fray in this phase.
The first-phase of the five-phase polling for thirteen constituencies had concluded on November 30.
The rest of the three phases will be held on December 12, 16 and 20.
Counting of votes will take place on December 23.