不一定的，也可以不倒裝。

例如句子:

Only you can clean the house。

意思是:只有你能清潔房子。

1.“only+狀語（副詞、介詞短語、從句等）”放在句首時，句子要用倒裝語序。如：

Only here were the police visible in any strength at all

只有在這裡才能看到廖廖幾個警察。(摘錄自《柯林斯高階英漢雙解學習詞典》)

Only in this way can we learn English. 只有這樣才能學會英語。

Only then did I understand what she meant. 只有到那時我才明白她的意思。

Only when he is selfless can a man be fearless. 只有無私，才能無畏。

Only if a teacher has given permission is a student allowed to enter this room. 只有得到教師的允許，學生才可以進這間屋。

Only by shouting was he able to make himself heard. 他只有叫喊才能讓別人聽到他。

注意1，在only後作狀語的是從句即使位於句首時，從句始終不要用倒裝，要部分倒裝的是主句。如：

Only when it rains do you feel cool. 只有下雨時才覺得涼爽一點。

Only when he returned home did he realize what had happened. 當他回到家裡時，才知道出了什麼事。

Only when we landed did we see how badly the plane had been damaged. 我們只是在著陸之後才看到飛機損壞的嚴重程度。

Only after she died was I able to appreciate her.

只有到她死後我才認識到她的價值。

注意2，only和所修飾的狀語如果不在句首，則不倒裝。

如：

The boy was helped out only when his father arrived in a hurry．

那男孩只有在父親匆忙趕到時才得到幫助。（不要倒裝）

Only then did he realize the importance of English

只有在那時候他才意識到英語的重要性。（要倒裝）

2.即使所處位置在句首，若only後接的不是狀語，而是主語或賓語，則通常無需倒裝。如：

Only the teachers are allowed to use the room．

只有老師們才可以用那個房間。

Only five men were hurt in the accident． Only those who had booked in advance were allowed in. 只有那些預先訂票的人可以進去。

Only part of his story is true. 他說的事只有部分是真的。

Only his sister he saw there. 他在那兒只看到他妹妹。

Only a policeman the children saw in the street.

孩子們在街上只看到一個警察。

Only the President could authorize the use of the atomic bomb

只有總統才能授權使用原子彈。(摘錄自《柯林斯高階英漢雙解學習詞典》)

Only a minority of the people supported the Revolution.

只有少數人支援這場革命