Biggest steelmaker Hoa Phat Group brought its prices of rolled steel and rebar steel down for the eighth time last weekend, bring prices down by VND2.4 million ($102.61) since mid-May.
Other steelmakers like Viet Nhat, Viet Y, Kyoei and Pomina have also brought down prices in the last two months.
The decline of steel prices came amid weaker demand and falling input prices.
Domestic steel demand in the first five months dropped by 6 percent year-on-year, according to stock brokerage SSI Research.
Steel production in April and May fell by 32 percent year-on-year, it added.
SSI Research said the rising prices of construction materials have delayed infrastructure projects, which could be part of the reason why steel prices have dropped.
Tightened policy on property development has also affected steel prices, it added.
Hot-rolled coil prices have dropped by 15-20 percent in China and the U.S. in the last three months due to declining construction and manufacturing activities.
Prices of coke, one of the input materials for steel, have dropped by 36 percent from its peak in March, while prices of iron ore have fallen 13 percent in the last three months, SSI Research said.
Another brokerage, VNDirect, expects steel consumption to recover next year thanks to public investment and recovery of the residential property market.